JP2006269657A - Method for manufacturing resin bonding type permanent magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate bridging of a composite material within a feeder, to realize smooth filling, and, for example, enable high-speed molding. <P>SOLUTION: The method includes: supplying a mixed composite material 8 of magnetic powder and resin material into a mold cavity 2 by reciprocating movement of a feeder 6; and compressing/molding a resin bonding type permanent magnet. When supplying the composite material 8 by the reciprocating movement of the feeder 6, an intermediate rod 5 is arranged in the mold cavity 2, and it is moved up and down to insert its tip into a housing space 7 of the composite material in the feeder 6. Thus, the bridging of the composite material 8 is eliminated within the feeder 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a resin-bonded permanent magnet made of a composite material obtained by mixing magnetic powder and a resin material, and relates to a technique for realizing smooth filling of the composite material.

  In recent years, resin-bonded permanent magnets (so-called bonded magnets) made of a composite material in which magnetic powder (magnet powder) and a resin material are mixed are easier to form into, for example, a cylindrical shape than sintered magnets. The use for motors and actuators for household appliances and industrial equipment is progressing. In particular, weight reduction is being promoted in small motors, actuators, and the like, and the resin-bonded permanent magnet is advantageous over the sintered magnet in this respect as well.

  By the way, even in resin-bonded permanent magnets, higher performance has been promoted, and rare earth magnetic powders such as SmCo magnetic powders and NdFeB magnetic powders are used as magnetic powders instead of ferrite magnetic powders conventionally used. It is becoming used. Further, as the motor is further reduced in size and performance, etc., the resin-bonded permanent magnet used is required to have higher characteristics while being thinner.

  In order to improve the performance of the resin-bonded permanent magnet, compression molding advantageous for improving the molding density is considered suitable, but when the thickness of the resin-bonded permanent magnet to be molded is 0.5 mm or less, Compression molding becomes very difficult. In particular, when considering the formation of a ring-shaped resin-bonded permanent magnet with a thin wall and a relatively long length, it is difficult to smoothly fill the composite material, and the resin has excellent magnetic properties and crushing strength. It is difficult to produce a coupled permanent magnet.

  Under such circumstances, a technique for smoothly filling a mold cavity with a composite material during compression molding has been studied (see, for example, Patent Document 1). The invention described in Patent Document 1 provides a method of eliminating bridging in a cavity and uniformly filling a powder, and a press mold thereof. Specifically, a die in which a cavity-forming through-hole is formed, a lower punch that is inserted into the through-hole and forms a cavity for a powder for a ring-shaped powder molded body, and the lower punch is vertically Ring-shaped powder to a press mold comprising a movably inserted lower core and a vertically movable upper punch having an outer shape fitted into the cavity and having a guide hole for accommodating the lower core In the powder filling method of the molded body, the lower core is rotated and / or vertically oscillated to fill the powder for ring-shaped powder molding.

That is, in the invention described in Patent Document 1, the lower core is moved up and down in the cavity space so that the supplied powder does not cause bridging in the cavity space and the powder is evenly filled in the cavity space. To be.
JP-A-8-332597

  However, according to the study by the present inventors, it has been found that the technique described in Patent Document 1 does not function effectively particularly during high-speed molding, and it is not always possible to realize a sufficient filling speed and filling property. . And the cause was presumed to be caused by the occurrence of a bridge in the composite material in the composite material accommodation space of the feeder when performing high-speed molding. In the technique described in Patent Document 1, since the lower core is merely moved up and down in the cavity space, it does not effectively act on the bridge of the composite material in the composite material accommodation space of the feeder.

  The present invention has been proposed for the purpose of eliminating the disadvantages of the prior art, and can eliminate the bridge of the composite material in the composite material accommodation space of the feeder. It is an object of the present invention to provide a method for producing a resin-bonded permanent magnet that realizes good filling properties and is capable of producing a resin-bonded permanent magnet excellent in magnetic properties and crushing strength.

  In order to achieve the above-described object, the method for producing a resin-bonded permanent magnet according to the present invention supplies a composite material obtained by mixing magnetic powder and a resin material into a mold cavity by reciprocating motion of a feeder, and performs compression molding. A method for manufacturing a resin-bonded permanent magnet, wherein a composite rod is disposed in the mold cavity when supplying a composite material by reciprocating motion of the feeder, and a tip of the intermediate rod is located in a composite material accommodation space of the feeder. The middle rod is moved up and down so as to be inserted into the head.

  In the method for producing a resin-bonded permanent magnet of the present invention, after magnetic powder and a resin material are mixed to form a composite material, this composite material is supplied into a mold cavity by reciprocating motion of a feeder. At this time, for example, when the molding speed is increased, a bridge of the composite material is generated in the composite material accommodation space of the feeder, thereby preventing smooth filling. This is particularly noticeable when the opening of the mold cavity is narrow.

  Therefore, in the present invention, an intermediate rod is installed in the mold cavity, and the intermediate rod is moved up and down so that the tip of the intermediate rod is inserted into the composite material accommodation space of the feeder. If an intermediate rod is inserted into the composite material accommodation space of the feeder and moved up and down, a physical force is directly applied to the composite material in the feeder. Therefore, even if the composite material has caused a bridge in the composite material accommodation space of the feeder, the bridge is quickly eliminated by the vertical movement of the center rod, and the smooth filling of the composite material into the mold cavity is realized. The

  According to the manufacturing method of the present invention, the bridge of the composite material generated in the composite material accommodation space of the feeder can be quickly eliminated, and the molding composite material can be smoothly guided into the mold cavity. Therefore, for example, it is possible to realize a good filling property even when molding at a high speed, and it is possible to manufacture a resin-bonded permanent magnet excellent in magnetic characteristics, crushing strength, and the like.

  Hereinafter, a method for producing a resin-bonded permanent magnet to which the present invention is applied will be described in detail with reference to the drawings.

  In the method for producing a resin-bonded permanent magnet of the present invention, the resin-bonded permanent magnet is compression-molded in a molding process after a resin material is added to and mixed with a magnetic powder pulverized to a predetermined particle size to form a composite material. By this, it is formed into a predetermined shape.

  Here, examples of the magnetic powder to be used include ferrite magnet powder (for example, Sr-based ferrite powder and Ba-based ferrite powder) and rare earth metal magnet powder (for example, SmCo-based, NdFeB-based, SmFeN-based, etc.). it can. What is necessary is just to select according to the characteristic requested | required from these. In particular, rare earth metal magnet powder is suitable for producing a high-performance resin-bonded permanent magnet.

  The rare earth metal magnet powder is mainly composed of a rare earth element, and the magnet composition is, for example, R-T-B (where R is one or more of rare earth elements, where the rare earth element includes Y). T is one or more of transition metal elements essentially containing Fe or Fe and Co, and B is boron.) In the case of a rare earth metal magnet powder, from the viewpoint of magnetic properties and the like, For example, the composition is preferably such that the rare earth element R is 10 to 30 atomic%, the boron B is 2 to 28 atomic%, and the balance (42 to 90 atomic%) is the transition metal element T. Here, R is one or more selected from rare earth elements, that is, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu. Especially, since Nd is abundant in resources and relatively inexpensive, the main component is preferably Nd.

  Or it is also possible to add the additive element M and to make an RTBM rare earth metal magnet powder. In this case, examples of the additive element M include Al, Cr, Mn, Mg, Si, Cu, C, Nb, Sn, W, V, Zr, Ti, Mo, Bi, and Ga. A seed | species or 2 or more types can be selected and added. The addition amount of these additive elements M is preferably 10 atomic% or less in total in consideration of magnetic characteristics such as residual magnetic flux density. If the amount of additive element M added is too large, the magnetic properties may be deteriorated.

  The form and particle size of the magnetic powder are arbitrary, and the shape and size of the resin-bonded permanent magnet to be manufactured, as well as the performance such as magnetic characteristics and mechanical characteristics required for the resin-bonded permanent magnet to be manufactured. You may choose according to. In particular, in order to increase the filling property of the magnetic powder, for example, to increase the crushing strength when it is molded into a ring shape, it is preferable to use a scaly magnetic powder. The scaly magnetic powders are filled in an overlapping manner and exhibit excellent filling properties. The magnetic powder preferably has an average particle size of 10 μm to 200 μm and a maximum particle size of 500 μm or less.

  On the other hand, as the resin material, a thermosetting resin is preferable, and for example, an epoxy resin or a phenol resin is preferable. Of course, the present invention is not limited to this, and any resin material known as a resin material used for this kind of resin-bonded permanent magnet can be used.

  When manufacturing a resin-bonded permanent magnet, first, the magnetic powder and the resin material are mixed in a mixing step. The mixing may be performed by a method such as wet mixing in which the resin material is diluted with an organic solvent and mixed with magnetic powder. In this case, general-purpose solvents such as acetone, toluene, methyl ethyl ketone, and methyl isobutyl ketone can be used as the organic solvent.

  The addition amount of the resin material in the mixing step is preferably 1.0% by mass to 5.0% by mass with respect to the magnetic powder. If the resin material is too much beyond the above range, the proportion of the magnetic powder relatively decreases, and there is a possibility that sufficient magnetic properties cannot be obtained. On the other hand, if the amount of the resin material added is too small, there is a possibility that the magnetic powder cannot be sufficiently bound, and the strength or the like may become a problem in the molded resin-bonded permanent magnet.

  After completion of the mixing step, the powder is separated into a molding powder in a predetermined particle size range and a coarse powder having a larger particle size than that in a classification step as necessary. The classification range is, for example, 30 μm to 150 μm (average particle size of about 100 μm), and magnetic powder having a particle size exceeding 150 μm is separated as a coarse powder.

  In the molding step, the molding powder in the predetermined particle size range is used as a molding material (composite material), and this is compression-molded into a predetermined shape using a mold, for example. At this time, the shape, size, etc. of the resin-bonded permanent magnet to be molded are arbitrary. For example, a cylindrical shape (ring shape) along the shape of the motor or actuator used, or a shape having a circular arc surface (tile shape) ) Etc. are typical. In particular, the present invention is used when the ring magnet is thin (for example, about 0.5 mm or less) and long (for example, 3.0 mm or more) ring-shaped magnet [for example, outer diameter (diameter) of about 3 mm to 5 mm]. This manufacturing method is effective.

In the molding, the compression molding pressure is preferably 784 MPa (8 tf / cm ² ) or more, and more preferably 980 MPa (10 tf / cm ² ) or more. By increasing the compression molding pressure, it is possible to increase the density of the resin-bonded permanent magnet.

  By the way, at the time of the compression molding, for example, when a long ring magnet having a small thickness is formed, the molding space (cavity) of the mold is a slit-like space having a small opening area. It is difficult to fill such a slit-like space with a small opening area with the composite material. In addition to this, when using, for example, scaly magnetic powder and performing high-speed molding such as 60 pieces per minute, for example 120 pieces per minute, in the composite material accommodation space of the feeder that supplies the composite material In this case, a bridge is generated in the composite material, which makes the filling more difficult.

  Therefore, in the present invention, an intermediate rod is installed in the molding space (die cavity), and the bridge of the composite material is eliminated in the composite material accommodation space of the feeder using the intermediate rod, and the opening area Will improve the fillability of the composite material in a small mold cavity.

  FIG. 1 shows an example of a molding apparatus for realizing the manufacturing method of the present invention. In the molding step, the composite material in the feeder is filled into the cavity 2 of the mold 1 called a mortar mold, and compression molding is performed. Therefore, after filling the composite material into the cavity 2 of the mold 1, the upper punch 3 and the lower punch 4 are inserted from above and below, and compression molding of the composite material is performed by these.

  The lower punch 4 is provided with an intermediate rod 5 passing through the lower punch 4 and inserted into the mold cavity 2. For example, when forming a ring-shaped resin-bonded permanent magnet, the center rod 5 plays a role of forming a center hole. In this case, the outer diameter of the center rod 5 is set to a ring-shaped resin-bonded magnet. It is set according to the inner diameter dimension.

  The middle rod 5 is movable up and down with respect to the lower punch 4 by an air cylinder or the like, for example, and can move up and down in the direction of an arrow y in the figure to perform so-called tapping. The range of the vertical movement of the center rod 5 is not limited to the depth range of the mold cavity 2, and the top end of the center bar 5 is moved up and down above the upper end surface of the mold 1 which is a mortar mold. Is possible.

  On the other hand, the supply of the composite material into the mold cavity 2 is performed by a feeder 6 as shown in FIG. The bottom surface of the feeder 6 is open. When the feeder 6 is reciprocated on the mold cavity 2 in the direction of the arrow x, the composite material 8 in the composite material accommodation space 7 is moved from the open bottom surface into the mold cavity 2. To fall and filling.

  However, if the composite material 8 forms a bridge in the composite material accommodation space 7 of the feeder 6 as described above, smooth filling is difficult. Therefore, as shown in FIG. 2, the tip of the middle rod 5 is protruded from the mold cavity 2 and enters the composite material accommodation space 7. In this state, the middle bar 5 is moved up and down (tapping). Thereby, the bridge | bridging of the said composite material 8 is eliminated, and the composite material which is a shaping | molding material falls into the mold cavity 2 rapidly. Further, the middle rod 5 moves up and down in the mold cavity 2, and as a result, contributes to improving the filling property of the composite material 8 in the mold cavity 2.

  The middle rod 5 needs to be moved up and down while the feeder 6 is reciprocating on the mold cavity 2. In this case, it is preferable that the number of vertical movements (tapping number) of the middle rod 5 is 1 to 5 times. In the case of high-speed molding, since the time during which the feeder 6 exists on the mold cavity 2 is short, it is necessary to perform tapping quickly during this time. Usually, the operation of the feeder 6 is controlled by a cam, and one filling operation by the feeder 6 is completed by rotating the cam once. The feeder 6 is present on the mold cavity 2 at a cam rotation angle of about 90 °, which is 1/4 of one cam rotation. Accordingly, when molding 60 pieces or more per minute, for example, 120 pieces per minute, the number of tapping / tapping time of the middle rod 5 is 1 to 5 times / [(60 seconds / 120 pieces) / 4]. In terms of frequency, it is 8 to 40 Hz.

  Further, the amplitude of the vertical movement of the middle bar 5 is preferably 0.5 mm to 15 mm. If the amplitude of the vertical movement of the middle bar 5 is less than 0.5 mm, the bridge may not be sufficiently eliminated. On the contrary, when the amplitude of the vertical movement of the center rod 5 exceeds 15 mm, the mechanical operation becomes large, and the mechanism for moving the center rod 5 up and down becomes large. In the case of high-speed molding, the operation of the feeder 6 is increased. It may be difficult to follow and operate at high speed.

  After filling the composite material 8 with the feeder 6, the feeder 6 is retracted from the mold cavity 2. At this time, the tip of the middle bar 5 is retracted until it is substantially flush with the upper surface of the mold 1 (upper surface of the mold cavity 2). Next, as shown in FIG. 3, the composite material 8 filled with the upper punch 3 and the lower punch 4 is compression-molded. The upper punch 3 is formed with an insertion hole (or a through-hole) 3a so that the tip of the middle rod 5 can be inserted. Thereby, a ring-shaped resin-bonded mold in which a center hole is formed by the middle rod 5 Permanent magnets (ring-shaped bonded magnets) can be formed. When the insertion hole (or the through hole) 3a is not formed in the upper punch 3, the center rod 5 follows the pressing of the upper punch 3 during the compression molding by the upper and lower punches 3 and 4. As the upper punch 3 is pushed in, the tip surface may be retracted in contact with the upper punch 3. As a result, there is no possibility of the composite material 8 being squeezed between the insertion hole or the through hole and the middle rod 5, and effective compression molding becomes possible.

  Next, specific examples of the present invention will be described based on experimental results.

Example NdFeB rare earth metal magnet powder [minor axis 20 μm, major axis 100 μm (maximum diameter 150 μm), scaly powder having a thickness of about 5 μm] was used as a magnetic powder, and 3 mass% of epoxy resin was added thereto to form a composite material . Compression molding was performed using this composite material. The molded resin-bonded permanent magnet has a ring shape (thickness 0.4 mm) having an outer diameter of 3.8 mm, an inner diameter of 3.0 mm, and a length of 6.0 mm.

  In molding, the molding apparatus shown in FIGS. 1 to 3 was used, and the tip portion of the center rod was inserted into the feeder, and the mold cavity was filled with the composite material while moving up and down (tapping). The number of tappings was set to twice at each filling. As a result, 120 pieces could be formed per minute. Moreover, as shown in Table 1, the molded ring-shaped resin-bonded permanent magnet was excellent in magnetic properties, crushing strength, and molded body density.

Comparative Example 1
As in the previous example, NdFeB rare earth metal magnet powder [minor axis 20 μm, major axis 100 μm (maximum diameter 150 μm), scaly powder having a thickness of about 5 μm] was used as the magnetic powder, and 3% by mass of epoxy resin was added thereto. Composite material.

  Tapping with the intermediate rod was not performed, and the same resin-bonded permanent magnet as in the example was molded. However, there was almost no problem in the filling property, and the molding speed was set to 20 pieces per minute in order to obtain excellent magnetic properties, crushing strength, and compact density as in the examples. In this case, the molding speed was slow and the productivity was poor.

Comparative Example 2
As in Comparative Example 1, the resin-bonded permanent magnet was molded in the same manner as in the example without performing tapping with the intermediate rod. The molding speed was 120 pieces per minute as in the example. In this case, the mold cavity was not sufficiently filled, many deformed products were generated, and the normal form of the resin-bonded permanent magnet could hardly be formed.

Comparative Example 3
The center rod was tapped only in the mold cavity, and molding was performed in the same manner as in the example. In this case, the density of the molded body was varied in each molded body due to defective filling into the mold cavity, and the yield was greatly reduced as compared with the example.

  Table 1 shows the number of cam rotations (number of moldings per minute), number of tappings, product strength of the obtained molded body (resin-bonded permanent magnet), fillability, and molded body density in Examples and Comparative Examples. Show. In Comparative Example 2, molding was almost impossible, and each data could hardly be measured.

It is a schematic sectional drawing which shows an example of the shaping | molding apparatus to which this invention is applied. It is a schematic sectional drawing which shows the center rod insertion state in the composite material accommodation space of a feeder. It is a schematic sectional drawing which shows a compression molding state.

Explanation of symbols

1 mold, 2 mold cavity, 3 upper punch, 4 lower punch, 5 center rod, 6 feeder, 7 composite material accommodation space, 8 composite material

Claims (10)

A composite material in which magnetic powder and a resin material are mixed is supplied into a mold cavity by a reciprocating motion of a feeder, and is a method for manufacturing a resin-bonded permanent magnet for compression molding,
When supplying the composite material by the reciprocating motion of the feeder, an intermediate rod is disposed in the mold cavity, and the intermediate rod is moved up and down so that the tip of the intermediate rod is inserted into the composite material accommodation space of the feeder. A method for producing a resin-bonded permanent magnet.   The method for producing a resin-bonded permanent magnet according to claim 1, wherein the vertical movement of the intermediate rod is performed 1 to 5 times during the supply of the composite material.   The method for producing a resin-bonded permanent magnet according to claim 1, wherein the amplitude of the vertical movement of the center rod is 0.5 mm to 15 mm.   The resin according to any one of claims 1 to 3, wherein the compression molding is performed by retracting the center rod so that a tip surface of the center rod is substantially flush with an upper end surface of the mold cavity. A manufacturing method of a combined permanent magnet.   The method for producing a resin-bonded permanent magnet according to any one of claims 1 to 4, wherein the resin-bonded permanent magnet is molded at a molding speed of 60 or more per minute.   The amount of the resin material added when mixing the magnetic powder and the resin material is 1.0 to 5.0% by mass with respect to the magnetic powder. A method for producing a resin-bonded permanent magnet according to Item.   The method for producing a resin-bonded permanent magnet according to claim 1, wherein the magnetic powder is a scaly powder.   The method for producing a resin-bonded permanent magnet according to claim 1, wherein the magnetic powder has an average particle size of 10 to 200 μm.   The method for producing a resin-bonded permanent magnet according to any one of claims 1 to 8, wherein the magnetic powder is a rare-earth magnet powder.   The method for producing a resin-bonded permanent magnet according to claim 1, wherein the resin material is a thermosetting resin.

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