JP4858708B2 - Powder molding equipment, molding die and permanent magnet - Google Patents

Description

  The present invention relates to an apparatus for producing a C-shaped molded body by pressure-molding raw material powder, and more particularly to a powder molding apparatus capable of chamfering the edge of the molded body.

Ferrite (sintered) magnets are relatively inexpensive and have high magnetic properties, and are therefore used in large quantities in a wide range of fields such as automobiles, home appliances, and industrial machines.
In order to produce a ferrite magnet, a mixture of raw materials at a predetermined mixing ratio is calcined to be ferritized, and the obtained calcined body is pulverized to a submicron size to obtain a finely pulverized powder composed of ferrite particles. . Next, the finely pulverized powder is compression-molded by a mold in a magnetic field (hereinafter referred to as magnetic field molding) to obtain a compact, and then the compact is sintered to obtain a ferrite magnet.
The magnetic field forming process is roughly divided into a dry type in which the material is dried and then formed, and a wet type in which the material is formed into a slurry. Since the wet molding is easier to align with the applied magnetic field, high magnetic properties can be obtained. In wet molding, slurry is pumped and filled into a cavity of a mold, and molding is performed while excluding liquid from the cavity by pressurizing in a magnetic field. Usually, a filter body is disposed on the upper punch side constituting the mold, and liquid is removed through the filter body.

  Patent Document 1 discloses a method of chamfering an edge portion on the filter body side, which is a molded body (magnet) obtained by wet molding. If the edge is sharp, chipping is likely to occur when assembling a ferrite magnet in a motor or other product, and it will be caught by a member to be assembled at the time of assembly, resulting in trouble in the assembly. Therefore, Patent Document 1 proposes chamfering the edge portion on the filter body side. Hereinafter, a wet molding apparatus disclosed in Patent Document 1 and a molded body (permanent magnet) obtained using the wet molding apparatus will be described with reference to FIGS. 6 and 7.

FIG. 6 is a cross-sectional view showing a schematic configuration of the wet molding apparatus.
In FIG. 6, the wet forming apparatus includes a die 111 supported on the floor by a support column 12, an upper punch 113 disposed so as to be movable up and down with respect to the die 111, and capable of being lifted and lowered in a through hole of the die 111. A lower punch 14 disposed opposite to the punch 113 is provided. The die 111, the upper punch 113, and the lower punch 14 constitute a mold. The upper punch 113 and the lower punch 14 can be moved up and down by cylinders 16 and 17, respectively.
A magnetic field coil 15 is disposed on the outer periphery of the die 111. Using this magnetic field coil 15, an orientation magnetic field is applied to the finely pulverized powder filled in the mold.

  In the wet molding apparatus, the upper punch 113 descends and comes into contact with the upper surface of the die 111, and the lower punch 14 rises in a through hole provided in the die 111 and performs pressure molding. The slurry containing the finely pulverized powder is filled into a cavity formed by the upper punch 113, the lower punch 14 and the die 111 and molded. A supply path 22 communicating with the cavity is formed in the die 111, and the slurry is supplied to the cavity through the supply path 22.

  The molding surface of the upper punch 113 forms the upper surface portion 102 of the permanent magnet (molded body) 101 shown in FIG. 7, and the molding surface of the lower punch 14 forms the lower surface portion 103. The upper punch 113 and the lower punch 14 are respectively formed with an arc-shaped concave portion and an arc-shaped convex portion that match the shape of the permanent magnet (molded body) 101 to be molded. Further, the upper punch 113 is provided with a plurality of drain holes 18, 18,... For disposing liquid pushed out from the slurry by pressurization to the outside, and the drain holes 18, 18,. 19 communicates. Further, a filter body 20 made of, for example, a filter cloth is attached to the upper punch 113 side, and pushes only the liquid into the drain hole 18 at the time of pressurization and functions to accumulate finely pulverized powder in the cavity. . The filter body 20 is wound around rolls 21 and 21, and is appropriately wound by the rotation of the rolls 21 and 21, so that continuous forming is possible without requiring replacement of the filter body 20. ing.

  FIG. 7 is a perspective view of the permanent magnet 101. The permanent magnet 101 is a permanent magnet called a C-shaped magnet or a segment magnet, and is mainly assembled as a magnetic force generation source in a motor. The permanent magnet 101 is curved in an arcuate shape, with the upper surface portion 102 constituting a weak magnetic surface and the lower surface portion 103 constituting a ferromagnetic surface. M is the easy axis direction of magnetization. The permanent magnet 101 is molded by the wet molding apparatus shown in FIG. 6, and chamfers 104 having a predetermined angle are formed at front and rear edge portions of the upper surface portion 102 which is a weak magnetic surface. An angle formed by the upper surface portion 102 and the chamfer 104 is defined as a chamfer angle. Patent Document 1 proposes that the chamfer angle be 10 to 45 degrees. In the present application, “a” of the permanent magnet 101 is defined as a length and “b” is defined as a width, and the direction corresponding to the length (a) of the permanent magnet 101 is defined as a length in the die 111, the upper punch 113, and the lower punch 14. The direction corresponding to the direction and width (b) will be referred to as the width direction.

A die 111 for forming a chamfer 104 on the permanent magnet 101 is shown in FIG. 8, and an upper punch 113 is shown in FIGS. 8A is a plan view of the die 111 (viewed from the molding surface side), FIG. 8B is a front view of the die 111, and FIG. 8C is a side view of the die 111. 9A is a plan view of the upper punch 113 (viewed from the molding surface side), FIG. 9B is a front view of the upper punch 113, and FIG. 9C is a side view of the upper punch 113. FIG. 10 is a perspective view of the upper punch 113 as viewed from the molding surface side.
As shown in FIG. 8, the die 111 includes a rectangular parallelepiped base 111a, and a rectangular parallelepiped through-hole 111b that forms a cavity is formed in the center of the die 111. In the base 111a, arc-shaped convex portions 111c having an arc shape are formed on both sides in the length direction of the through hole 111b. The die 111 is incorporated into the wet molding apparatus with the side on which the arcuate convex portion 111c is formed facing up. Both ends of the arc-shaped convex portion 111c in the width direction are continuous with the upper surface of the base portion 111a through the inclined surface 111d.

Next, as shown in FIGS. 9 and 10, the upper punch 113 includes a rectangular parallelepiped base portion 113 a. An arc-shaped recess 113b and two arc-shaped recesses 113c are formed on one surface side of the base 113a. The arc-shaped recess 113b is formed at the center of the upper punch 113 in the length direction. The arc-shaped recess 113c is disposed on each side of the arc-shaped recess 113b in the length direction. Both the arc-shaped recess 113b and the arc-shaped recess 113c are recessed in an arc shape in the width direction of the base 113a. The arc-shaped recess 113b is a part directly involved in molding. Further, the arc-shaped concave portion 113c comes into contact with the arc-shaped convex portion 111c of the die 111 during actual molding.
The arc-shaped recess 113b has a circular arc surface continuous with the surface of the base 113a at both ends in the width direction. Further, the arc-shaped recess 113c is continuous with the surface of the base 113a through the inclined surface 113d at both ends in the width direction. Further, both ends in the length direction of the arc-shaped recess 113b are connected to each other via the arc-shaped recess 113c and the inclined surface 113e.
The chamfer 104 of the permanent magnet 101 is formed along the inclined surfaces 113d and 113e of the upper punch 113 during molding.

Japanese Patent Publication No. 6-12727

According to the proposal of Patent Document 1, since the chamfers 104 can be formed at both end portions of the C-type permanent magnet 101, it is effective in preventing cracks and chipping during assembly into the motor. However, even in the permanent magnet 101 proposed in Patent Document 1, sharp edges are generated at both ends. It is a part shown by SE of FIG. This sharp edge SE is because the inclined surface 113e of the upper punch 113 does not have a predetermined width to both ends in the width direction. That is, the chamfer 104 cannot be formed on the portion corresponding to the inclined surface 113 d of the upper punch 113 due to the structure of the upper punch 113.
The present invention has been made based on such a technical problem, and provides a powder molding apparatus capable of forming a chamfer having a predetermined width over the entire circumference of the edge of a C-shaped permanent magnet. For the purpose.

In the upper punch 113 shown in FIGS. 9 and 10, if the inclined surface 113d is eliminated, the inclined surface 113e is also eliminated accordingly. The present inventors have studied the structure of the upper punch that can leave the inclined surface 113e without the inclined surface 113d.
In the upper punch 113 shown in FIGS. 9 and 10, both the arc-shaped recess 113b and the arc-shaped recess 113c are recessed with reference to the same plane. Therefore, in order to form the inclined surface 113e, the presence of the inclined surface 113d is indispensable, and the chamfer 104 having a predetermined width cannot be formed over the entire periphery of the edge portion of the C-shaped permanent magnet 101.

Therefore, in the present invention, in the upper punch, a reference surface (S1) in which the arc-shaped recess provided for molding is recessed and a reference surface (S2) in which the arc-shaped recesses disposed on both sides thereof are recessed are formed. The surface (S1) and the surface (S2) are not the same plane, but are parallel to each other, but the surface (S1) is retracted from the surface (S2) to provide a step corresponding to the inclined surface 113d. By doing so, it became possible to form a chamfer over the entire circumference of the edge of the C-shaped permanent magnet. That is, the present invention is a method of pressing a raw material powder into a C-shaped molded body having a width direction and a length direction, having an arc shape along the width direction, and having a convex surface and a concave surface facing the convex surface. A die having a through hole corresponding to the outer shape of the molded body, a die non-molding portion surrounding the periphery of the through hole, and a central axis direction of the through hole of the die. A lower punch that can be moved up and down, and an upper punch that is disposed to face the lower punch. The upper punch forms a convex surface of the molded body, forms a circular arc along the width direction of the molded body, and surrounds the molded surface and contacts the non-molded portion of the die during molding. And the molding surface of the upper punch has inclined surfaces that hang in the direction of the lower punch at both ends in the length direction of the molded body, and the upper punch non-molding portion is an inclined surface. A step corresponding to the inclined surface is formed at a portion continuous with the end portion in the width direction of the die, and the die non-molding portion has a trapezoidal projection portion, and the projection portion of the upper punch non-molding portion is formed at the time of molding . wherein the contacting with the step difference.

  In the powder molding apparatus of the present invention, by forming a step corresponding to the inclined surface in the portion where the upper punch non-molded portion is continuous with the end in the width direction of the inclined surface, the end in the width direction of the inclined surface is They can be arranged on a straight line along the length direction.

The present invention has a width direction and a length direction, has an arc shape along the width direction, and a C-shaped formed body having a convex surface and a concave surface facing the convex surface is formed by press-molding raw material powder. It can be regarded as a molding die used in the powder molding apparatus to be produced, and this molding die includes a through hole corresponding to the outer shape of the molded body and a die non-molding portion surrounding the through hole. A die, a lower punch capable of moving up and down along the direction of the central axis of the through hole of the die, and an upper punch disposed to face the lower punch, and the upper punch forms a convex surface of the molded body A molding surface having an arc shape along the width direction of the molded body, and an upper punch non-molding portion that surrounds the molding surface and contacts the die non-molding portion at the time of molding. At both ends in the length direction, there are inclined surfaces that hang down in the direction of the lower punch, The part is formed with a step corresponding to the inclined surface at a portion continuous with the end portion in the width direction of the inclined surface, and the die non-molding portion has a trapezoidal protruding portion, and the protruding portion is wherein the contacting with the step difference of the punch unformed section.
Also in this mold, the upper punch non-molding portion forms a step corresponding to the inclined surface in a portion that is continuous with the widthwise end of the inclined surface. They can be arranged on a straight line along the vertical direction.

  According to the present invention, a chamfer with a predetermined width can be formed over the entire circumference of the edge of the C-shaped molded body (permanent magnet).

Hereinafter, the wet molding apparatus according to the present embodiment will be described with reference to the drawings.
The wet molding apparatus according to the present embodiment has a basic configuration as shown in FIG. Therefore, the description of the basic configuration is omitted here, and the configuration of the die and the upper punch, which are features of the present embodiment, will be mainly described.

  A die 11 according to this embodiment is shown in FIG. 1, and an upper punch 13 is shown in FIGS. 1A is a plan view of the die 11, FIG. 1B is a front view of the die 11 (viewed from the molding surface side), and FIG. 1C is a side view of the die 11. 2A is a plan view of the upper punch 13 (viewed from the molding surface side), FIG. 2B is a front view of the upper punch 13, and FIG. 2C is a side view of the upper punch 13. FIG. 3 is a perspective view of the upper punch 13 as viewed from the molding surface side. The die 11 is replaced with the die 111 of the wet forming apparatus shown in FIG. 6, and the upper punch 13 is replaced with the upper punch 113 of the wet forming apparatus shown in FIG. 6 to constitute the wet forming apparatus. 1 to 3 show only main parts of the die 11 and the upper punch 13.

As shown in FIG. 1, the die 11 includes a rectangular parallelepiped base portion 11a, and a rectangular parallelepiped through-hole 11b forming a cavity is formed in the center portion thereof.
In the base portion 11a, arc-shaped convex portions 11c are formed on both sides in the length direction of the through hole 11b. The arcuate convex portion 11c has an arcuate surface that protrudes from the reference surface 11S (die non-molding portion) on the upper surface of the base portion 11a and has a maximum height at the center in the width direction. This arc-shaped surface constitutes a molding surface.
The base portion 11a has trapezoidal protrusions 11d on both sides in the width direction of the through hole 11b. The upper surface of the protrusion 11d protrudes from the reference surface 11S by a predetermined height.
The die 11 is assembled into the wet molding apparatus with the side on which the arc-shaped convex portion 11c is formed facing upward.

Next, the upper punch 13 will be described with reference to FIGS.
As shown in FIGS. 2 and 3, the upper punch 13 includes a rectangular parallelepiped base portion 13 a.
An arcuate recess 13b and two arcuate recesses 13c are formed on one surface (molding surface) side of the base 13a. The arcuate recess 13b is formed in the center of the upper punch 13 in the length direction. The arc-shaped recess 13c is disposed on each side of the arc-shaped recess 13b in the length direction. Both the arc-shaped recess 13b and the arc-shaped recess 13c are recessed in an arc shape in the width direction of the base portion 13a. The arcuate recess 13b forms a molding surface that is directly involved in molding. The arcuate recess 13c corresponds to the arcuate protrusion 11c of the die 11, and the arcuate recess 13c contacts the arcuate protrusion 11c of the die 11 during actual molding.

  The arcuate recess 13b is connected to the reference surface 13S1 (the upper punch non-molding part) of the base part 13a at both ends in the width direction. Further, the arc-shaped concave portion 13c is continuous with the reference surface 13S2 (the upper punch non-molded portion) of the base portion 13a at both ends in the width direction. The reference surface 13S1 is formed to recede from the reference surface 13S2, and there is a step between the reference surface 13S1 and the reference surface 13S2.

The arc-shaped recess 13b and the arc-shaped recess 13c are connected via the inclined surface 13e. Now, as shown in FIG. 3, let two circular arcs which divide the inclined surface 13e be 13e1 and 13e2. The arc 13e1 is located at the boundary between the arcuate recess 13b and the inclined surface 13e. Further, the arc 13e2 is located at the boundary between the arcuate recess 13c and the inclined surface 13e. If the distance between the arc 13e1 and the arc 13e2 is the width of the inclined surface 13e, the inclined surface 13e can have a predetermined width (constant in this example) from one end to the other end. The inclined surface 13e is an inclined surface that hangs down from the arcuate recess 13b toward the lower punch 14 (or the arcuate recess 13c) in a state where the upper punch 13 is incorporated in the wet molding apparatus.
Further, the reference surface 13S1 and the reference surface 13S2 are connected via an inclined surface 13d. The inclined surface 13d also becomes an inclined surface that hangs down from the reference surface 13S1 toward the reference surface 13S2 in a state where the upper punch 13 is incorporated in the wet molding apparatus.

The inclined surface 13e is continuous with the inclined surface 13d at both ends thereof. As described above, a step is formed between the reference surface 13S1 and the reference surface 13S2. By making this step correspond to the inclined surface 13e, particularly the width thereof, the inclined surface 13e extends from one end to the other end. It can have a predetermined width. Note that this step may be formed at least in a portion where the inclined surface 13e and the inclined surface 13d are continuous.
In the case of the present embodiment, one end of the arc 13e1 and one end of the arc 13e2 are arranged on a straight line along the length direction. This straight line indicates the boundary between the arcuate recess 13b and the reference surface 13S1, and the boundary between the arcuate recess 13c and the reference surface 13S2.

FIG. 4 shows a cross-sectional view of a state in which pressure forming is performed using the die 11, the upper punch 13, and the lower punch 14. 4A is a front cross-sectional view at the center in the length direction, and FIG. 4B is a side cross-sectional view at the center in the width direction.
As shown in FIGS. 4A and 4B, the lower punch 14 is disposed at a predetermined position in the through hole 11 b of the die 11. The upper punch 13 is opposed to the lower punch 14 at a predetermined interval, and the reference surface 13S1 or 13S2 thereof is in contact with the reference surface 11S of the die 11. In this manner, the slurry containing the finely pulverized powder is filled in the cavity formed by arranging the die 11, the upper punch 13 and the lower punch 14.

  FIG. 5 shows a C-type permanent magnet 1 obtained by using the mold according to the present embodiment. The permanent magnet 1 has the same basic configuration as the permanent magnet 101 shown in FIG. The difference between the two is in chamfer 4 and chamfer 104. That is, the permanent magnet 1 has a chamfer 4 having a constant width over the entire width direction of the upper surface portion 2, whereas the permanent magnet 101 has a smaller chamfer 104 width near both ends of the upper surface portion 102 in the width direction. Thus, the inclined surfaces are not formed at both ends. Therefore, the conventional permanent magnet 101 has a sharp edge SE, whereas the permanent magnet 1 according to the present embodiment does not have a sharp edge. If the sharp edge SE exists, when the C-type permanent magnet is incorporated in the motor casing, the sharp edge SE may be caught inside the casing, causing chipping or cracking. In order to prevent this, the sharp edge SE may be polished, but the manufacturing cost increases by polishing. Since the permanent magnet 1 according to the present embodiment does not have a sharp edge SE, it is not necessary to perform such polishing.

  FIG. 11 shows a modification of the upper punch 13. As shown in FIG. 11, the basic configuration of the upper punch 13 'according to this modification is the same as that of the upper punch 13 shown in FIGS. 2 and 3, but the form of the inclined surface 13d' is the same as that of the inclined surface 13d. Is different. However, the step corresponding to the inclined surface 13e 'coincides with the upper punch 13 in that it is formed in the non-molded portion of the upper punch 13'. Needless to say, the present invention includes the upper punch 13 'having the structure shown in FIG.

It is a three-plane figure which shows the dice | dies of this Embodiment, (a) is a top view of dice | dies, (b) is a front view of dice | dies, (c) is a side view of dice | dies. It is a three-plane figure which shows the upper punch of this Embodiment, (a) is a top view of an upper punch, (b) is a front view of an upper punch, (c) is a side view of an upper punch. It is the perspective view which looked at the upper punch of this Embodiment from the molding surface side. It is sectional drawing which shows the state currently pressure-formed using the die | dye of this Embodiment, an upper punch, and a lower punch, (a) is front sectional drawing, (b) is side sectional drawing. It is a perspective view which shows the C-type permanent magnet (molded object) obtained by this Embodiment. It is sectional drawing which shows the structure of a wet shaping | molding apparatus. It is a perspective view which shows the conventional C type permanent magnet (molded object). It is a three-plane figure which shows the conventional dice | dies, (a) is a top view of dice | dies, (b) is a front view of dice | dies, (c) is a side view of dice | dies. It is a three-plane figure which shows the conventional upper punch, (a) is a top view of an upper punch, (b) is a front view of an upper punch, (c) is a side view of an upper punch. It is the perspective view which looked at the conventional upper punch from the molding surface side. It is the perspective view which looked at the modification of the upper punch of this Embodiment from the molding surface side.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Die, 11a ... Base part, 11b ... Through-hole, 11c ... Arc-shaped convex part, 11d ... Projection part, 11S ... Reference plane, 13 ... Upper punch, 13a ... Base part, 13b, 13c ... Arc-shaped recessed part, 13d, 13e ... Inclined surface, 13e1, 13e2 ... Circular arc, 13S1, 13S2 ... Reference surface, 14 ... Lower punch

Claims (5)

A C-shaped molded body having a width direction and a length direction and having an arc shape along the width direction and having a convex surface and a concave surface facing the convex surface is produced by pressure-molding raw material powder. A powder molding apparatus,
A die provided with a through hole corresponding to the outer shape of the molded body, and a die non-molding portion surrounding the periphery of the through hole;
A lower punch capable of moving up and down along the central axis direction of the through hole of the die,
An upper punch disposed opposite to the lower punch,
The upper punch is
Forming the convex surface of the molded body, and a molding surface having an arc shape along the width direction of the molded body;
An upper punch non-molding part that surrounds the molding surface and contacts the die non-molding part during molding,
The molding surface has inclined surfaces depending on the direction of the lower punch at both ends in the length direction of the molded body,
The upper punch non-molded portion is formed with a step corresponding to the inclined surface at a portion continuous with the end portion in the width direction of the inclined surface,
The die unformed portion has a protruding portion of the trapezoidal, powder molding device to which the protruding portion is equal to or in contact with the front Stories step of the upper punch unformed portion during molding.   2. The powder molding apparatus according to claim 1, wherein end portions in the width direction of the inclined surfaces are arranged on a straight line along the length direction. A C-shaped molded body having a width direction and a length direction and having an arc shape along the width direction and having a convex surface and a concave surface facing the convex surface is produced by pressure-molding raw material powder. A mold used in a powder molding apparatus,
The molding die is
A die provided with a through hole corresponding to the outer shape of the molded body, and a die non-molding portion surrounding the periphery of the through hole;
A lower punch capable of moving up and down along the central axis direction of the through hole of the die,
An upper punch disposed opposite to the lower punch,
The upper punch is
Forming the convex surface of the molded body, and a molding surface having an arc shape along the width direction of the molded body;
An upper punch non-molding part that surrounds the molding surface and contacts the die non-molding part during molding,
The molding surface has inclined surfaces depending on the direction of the lower punch at both ends in the length direction of the molded body,
The upper punch non-molded portion is formed with a step corresponding to the inclined surface at a portion continuous with the end portion in the width direction of the inclined surface,
The die unformed portion has a protruding portion of the trapezoidal, forming mold where the projecting portion is equal to or in contact with the front Stories step of the upper punch unformed portion during molding.   4. The molding die according to claim 3, wherein end portions in the width direction of the inclined surfaces are arranged on a straight line along the length direction. A molded body having a width direction and a length direction, having an arc shape along the width direction, a convex surface, and a concave surface facing the convex surface, the molded body molded by the powder molding apparatus according to claim 1 or 2. permanent magnets, characterized in that Ru is obtained by sintering.

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