JP2012209484A - Bond magnet and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-density bond magnet by obtaining a sound green compact less susceptible to cracks even when base powder whose resin amount is reduced to 0.5-1.0 mass% is formed under high pressure.SOLUTION: The bond magnet obtained by binding magnet powder with resin has a cylindrical shape including a hollow part, in which a first layer P11 whose resin amount is 1.5-2.0 mass% is disposed at both end parts or one end part in an axial direction of the hollow part, and a second layer P12 whose resin amount is 0.5-1.0 mass% is disposed in the remaining part at a density of 6.4 Mg/mor more.

Description

The present invention relates to a bonded magnet obtained by binding magnet powder with a resin and a method for manufacturing the same, and more particularly to a bonded magnet having a cylindrical shape with a magnet density of 6.4 Mg / m ³ or more and a method for manufacturing the bonded magnet.

  Bonded magnets made by binding magnet powder with resin have a high degree of freedom in shape, and by using rare earth magnet materials such as neodymium magnets as magnet powder, high magnetic flux density and strong magnetic force can be exhibited. Used for sensors, it is used in a wide range of fields such as general household appliances, automobile parts, acoustic equipment, medical equipment, and general industrial equipment.

  The bonded magnet is given a product shape by a molding process. The molding process includes an injection molding method (such as Patent Document 1) in which magnet powder is injected and molded together with a plastic raw material into a mold having a product shape, and a raw material containing magnet powder and resin in the mold cavity. It is roughly classified into a compression molding method (Patent Document 2 or the like) in which powder is filled and compression molding is performed by upper and lower punches. These molding methods are properly used according to the application.

In the various devices described above, demands for improving magnetic properties such as magnetic flux density and maximum energy product (BH) _max have been increasing with respect to bonded magnets under recent demands for miniaturization and weight reduction. In this respect, although the injection molding method has a high degree of freedom in shape, it is necessary to impart plasticity to the raw material, so the amount of magnet powder occupying the raw material is limited, and magnetic properties such as magnetic flux density and maximum energy product (BH) _max are limited. It is difficult to meet the demand for improved characteristics. On the other hand, in the compression molding method, although the degree of freedom of shape is lower than that of the injection molding method, the content of the magnet powder can be increased, so that the magnetic flux density and the maximum energy product (BH) _max are excellent. A bonded magnet can be obtained.

  FIG. 1 shows a general molding process for molding a green compact of a bonded magnet having a hollow portion by a compression molding method. The mold apparatus shown in FIG. 1 has a die 1 having a mold hole 1a that forms the outer periphery and bottom surface of a green compact, a core rod 2 that forms a hollow portion of the green compact, and an upper surface of the green compact. And a punch 4. On the bottom surface forming side of the green compact, eject pins 31 for extruding the green compact after molding are arranged at equal intervals in the circumferential direction. Using such a mold apparatus, as shown in FIG. 1 (a), a cavity is formed by the mold hole 1a of the die 1 and the core rod 2, and the raw material powder M is fed into the cavity by means of powder supply such as a feeder 5. Fill. Next, as shown in FIG. 1B, the upper punch 4 is lowered, and the raw material powder M filled in the cavity is compression-molded by the upper punch 4 to obtain a green compact C. Thereafter, as shown in FIG. 1 (c), the upper punch 4 is moved upward to return to the standby position, and the eject pin 31 is moved upward to move the green compact C from the mold hole 1 a of the die 1. Extrude.

JP 2009-137138 A JP 2009-099580 A

The compression molding method can increase the content of the magnet powder in the raw material powder compared to the injection molding method, so it is easy to obtain a bonded magnet with excellent magnetic flux density. Improvement is desired. In order to improve the magnetic flux density and maximum energy product (BH) _max of the bonded magnet, it is necessary to increase the content ratio of the bonded magnet by increasing the content of the magnet powder and forming the raw material powder at a high density. Therefore, when forming the bonded magnet, it is necessary to reduce the resin amount of the raw material powder to increase the ratio of the magnet powder and to form the raw material powder at a high pressure.

Therefore, the inventors of the present invention reduced the amount of resin in the raw material powder to 0.5 to 1.0% by mass, and formed a green compact of the bonded magnet. The molding was performed under a high molding pressure of 1960 MPa by a one-press molding as shown in FIG. 1, and the raw material powder was compression molded into a cylindrical shape. However, as shown in FIG. 2, a crack occurred from the inner peripheral surface to the upper end surface at a position t from the upper end surface of the obtained green compact C ₁ . The upper end surface of the green compact is a surface pressed by the upper punch 4. This crack is considered to have occurred as follows. That is, since the magnet powder in the raw material powder is hard and hardly plastically deformed, the magnet powder in contact with the upper punch 4 and the magnet powder in the vicinity thereof are elastically deformed by pressurization from the upper punch 4. At this time, the pressing force from the upper punch 4 acts not only in the axial direction but also in a direction orthogonal to the axial direction, that is, in a direction in which the core rod 2 is compressed from its outer peripheral surface, and the core rod 2 is elastically deformed radially outward. In this state, compression molding is performed. Thereafter, when the pressure from the upper punch 4 is unloaded, the core rod 2 is considered that cracks are generated on the inner circumferential surface of the upper end face near the compact C ₁ elastically restored.

  Therefore, the present invention provides a green compact that is less prone to cracking even if the raw material powder with the resin content reduced to 0.5 to 1.0% by mass is molded under high pressure. An object of the present invention is to provide a bonded magnet having a high height.

The bonded magnet of the present invention is a bonded magnet obtained by binding magnet powder with a resin, and has a cylindrical shape having a hollow portion, and the amount of resin is 1. at both ends or one end in the axial direction of the hollow portion. A first layer of 5 to 2.0% by mass is provided, and a second layer having a resin amount of 0.5 to 1.0% by mass is provided in the balance, and the density is 6.4 Mg / m ³ or more. It is characterized by being.

  In this invention, since the 1st layer whose resin amount is 1.5-2.0 mass% is provided in the both ends or one edge part of the axial direction of the hollow part of a bonded magnet, the end at the time of compression molding The deformability of the part is high. For this reason, the deformation | transformation by the elastic return of the core rod after edge part shaping | molding can be absorbed, and generation | occurrence | production of the crack of an edge part can be prevented. Moreover, since the 2nd layer which reduced resin amount with 0.5-1.0 mass% is provided in remainder, the density ratio of a bond magnet can be made 80% or more, and a magnetic flux density can be made high. .

The amount of resin in the first layer is 1.5 to 2.0% by mass. If the amount of resin is less than 1.5% by mass, the elastic deformation of the core rod cannot be absorbed and cracks are likely to occur. On the other hand, if the amount of resin exceeds 2.0% by mass, the influence of a decrease in the amount of magnet powder in the raw material powder becomes large, and it becomes difficult to obtain desired magnetic properties. Moreover, even if the resin amount of the second layer is reduced to 0.5 to 1.0% by mass by setting the first layer to the above resin amount, cracks are generated at the end during compression molding. Can be prevented. If the amount of the resin in the second layer is too small, molding becomes difficult, so 0.5% by mass or more is required. On the other hand, if the amount of resin exceeds 1.0% by mass, the density of the magnet decreases and falls below 6.4 Mg / m ³ .

  In the bonded magnet of the present invention, in the axial direction, it is preferable that the height of the first layer is 1 to 3 mm and the height of the second layer is 9 mm or more. If the height of the first layer is less than 1 mm, the deformability at the time of compression molding cannot be obtained sufficiently, and it becomes difficult to prevent the occurrence of cracks at the end. And if the height of a 1st layer is 1-3 mm, the said effect is fully acquired and generation | occurrence | production of the crack of an edge part can be prevented reliably. Further, if the height of the second layer in the axial direction is less than 9 mm, the density ratio of the bonded magnet is lowered and the magnetic properties are deteriorated. For this reason, the higher the height of the second layer, the better, and 9 mm or more is preferable.

  In the bonded magnet of the present invention, the cylindrical shape having a hollow portion includes a hollow portion having a circular, elliptical, polygonal shape, etc., or a composite shape thereof. The strip includes one or a plurality of formed shapes. Further, the outer peripheral shape includes a circular shape, an elliptical shape, a polygonal shape, and the like, or a composite shape thereof, or includes a shape in which one or a plurality of concave stripes or convex stripes such as a key are formed.

  The first bonded magnet manufacturing method of the present invention uses a die device comprising a die having a die hole, a core rod, and an upper punch and a lower punch that are slidably fitted to the core rod and the die hole. A first filling step of filling a mold raw material hole, a core rod, and a cavity formed by a lower punch with a second raw material powder containing a magnet powder having a resin addition amount of 0.5 to 1.0% by mass; 2 Forming pressure 1470 ~ by the 2nd filling process which fills and laminates the 1st ingredient powder containing magnet powder whose addition amount of resin is 1.5-2.0 mass% on the raw material powder, and an upper punch A compression molding process in which the first and second raw material powders are compression-molded by one-press molding at 2450 MPa, an extrusion process in which the obtained green compact is extruded, and the green compact is heated to bind the magnet powder with a resin. And a heat treatment step.

  The second bonded magnet manufacturing method of the present invention uses a mold apparatus comprising a die having a mold hole, a core rod, and an upper punch and a lower punch that are slidably fitted to the core rod and the mold hole. A first filling step of filling a die raw material hole, a core rod, and a third raw material powder containing magnet powder having a resin addition amount of 1.5 to 2.0 mass% into a cavity formed by a lower punch; A second filling step of filling and laminating a second raw material powder containing a magnet powder having a resin addition amount of 0.5 to 1.0% by mass on the third raw material powder; In addition, the third filling step of laminating and laminating the first raw material powder containing the magnet powder having a resin addition amount of 1.5 to 2.0% by mass, and the upper punch and the lower punch at a molding pressure of 1470 to 2450 MPa The first, second and third raw material powders are compression-molded by double-press molding A compression molding step, the extrusion step of extruding the obtained green compact, and performing a heat treatment step of forming wear magnet powder with a resin by heating the green compact.

  According to the first and second methods for manufacturing a bonded magnet of the present invention, since the raw material powder needs to be compressed once, the manufacturing cost can be reduced. Moreover, since the raw material powder with a large amount of resin added is used at the end of the bonded magnet, the molding pressure can be increased while preventing the occurrence of cracks at the end. For this reason, the density of the bonded magnet can be increased and the magnetic flux density can be improved.

  In the first and second bonded magnet manufacturing methods of the present invention, the first raw material powder and the third raw material powder have a filling depth of 1 to 3 mm after compression molding, and the second raw material powder The preferred embodiment is that the filling depth is 9 mm or more after compression molding. Moreover, it is set as a preferable aspect that the 1st-3rd raw material powder consists of the resin coating magnet powder which coat | covered and provided resin on the surface of the magnet powder. In the present invention, the resin and magnet powder used in the first to third raw material powders may be the same or different. For example, the first and third raw material powders may be made of the same material, and the second raw material powder may be made of different materials.

If the molding pressure at the time of compression molding is less than 1470 MPa, the raw material powder cannot be sufficiently densified, and the density of the bonded magnet cannot be made 6.4 Mg / m ³ or more. On the other hand, even if compression molding is performed at a pressure exceeding 2450 MPa, the density improvement rate of the bonded magnet is small, and the mold is easily damaged. Therefore, the molding pressure is set to 1470 to 2450 MPa.

  The green compact is heated to bind the magnet powder with resin. The resin is cured by heating and the magnetic powder is bound to improve the strength of the bonded magnet. The heating temperature is equal to or higher than the curing temperature of the resin, and when thermal decomposition occurs, the strength decreases and the insulation of the magnet powder becomes poor.

  As resin, an epoxy resin, a phenol resin, a melamine resin, a polyimide resin etc. are mentioned, for example, 1 type (s) or 2 or more types are used. In addition, you may use together the hardening | curing agent suitable for each resin as needed. The resin may be added to the magnet powder in the form of powder, but it is preferable to coat the surface of the magnet powder by dissolving the resin with a solvent and drying.

  Moreover, as magnet powder, well-known magnet powders, such as rare earth magnet powder and a ferrite magnet powder, can be used individually or in mixture. Examples of rare earth magnet powders include Nd—Fe—B based magnet powder, Sm—Co based magnet powder, Sm—Fe—N based magnet powder, and the like.

  According to the present invention, it is possible to obtain a healthy green compact that does not easily generate cracks even when the raw material powder having a resin amount reduced to 0.5 to 1.0% by mass is molded under high pressure, A bonded magnet having a high density of the compact can be produced.

It is a schematic diagram which shows an example of the shaping | molding process in the manufacturing method of the conventional bond magnet, (a) is a filling process of raw material powder, (b) is a compression molding process of raw material powder, (c) is an extrusion process of a green compact. It is. It is a schematic diagram which shows the condition of the crack which generate | occur | produces in the manufacturing method of the conventional bond magnet. It is a mimetic diagram showing the bonded magnet of a 1st embodiment of the present invention. It is a schematic diagram explaining the shaping | molding process in the manufacturing method of the 1st bonded magnet of this invention, (a-1) and (a-2) are the 1st and 2nd filling process of raw material powder, (b) is a raw material. The powder compression molding process, (c) is the green compact extrusion process. It is a schematic diagram which shows the bonded magnet of 2nd Embodiment of this invention. It is a schematic diagram explaining the shaping | molding process in the manufacturing method of the 2nd bonded magnet of this invention, (a-1)-(a-3) is the 1st-3rd filling process of raw material powder, (b) is raw material powder. (C) is a green compact extrusion process.

(1) 1st Embodiment The bonded magnet of 1st Embodiment of this invention is shown in FIG. Bond magnet P1 of _1st Embodiment of this invention has the cylinder shape which has a hollow part, and the 1st layer P whose resin amount is 1.5-2.0 mass% on an upper end surface side (upper side of a figure). ₁₁ are mounted on the remaining portion, the second layer _{P 12} resin amount of 0.5 to 1.0 mass% is configured provided as the body.

Usually, in a bonded magnet having a large amount of resin, when a stress is applied, the resin is deformed to prevent the occurrence of cracks and the like. However, in a bonded magnet with a large amount of resin, the density ratio of the bonded magnet decreases as a result of the relatively decreased amount of magnet powder. Therefore, in the bonded magnet P ₁ of the first embodiment of the present invention, the upper end surface imparts the ability to absorb stress by increasing the amount of resin, when the elastic return of the mold core rod, absorb stress as a layer for preventing the occurrence of cracks and is provided with a first layer P _11. Therefore, the first layer P ₁₁ has less amount of resin amount is large magnet powder. The height d of the first layer P ₁₁ may be set larger than the crack generation position t from the top surface (see Figure 2 (b)). Specifically, a height of 1 mm or more is recommended.

On the other hand, the height H of the bonded magnet, which is determined from the specifications of the product, the height d of the first layer P ₁₁ is increased, correspondingly, the height h of the second layer P ₁₂ is a body As a result, the amount of magnet powder in the entire bonded magnet is reduced, and the magnetic properties are deteriorated. Therefore, the height d of the first layer _{P 11} is recommended to stop the 3mm or less. In order to increase the density ratio of the entire bonded magnet product, the height h is preferably as large as possible, and is recommended to be 9 mm or more.

The first layer P ₁₁ By setting the resin amount and height of the, also to reduce the resin amount of the second layer P ₁₂ is a body to 0.5-1.0 wt%, cracks at the time of compression molding Can be prevented. For this reason, the density ratio of the whole bonded magnet can be increased to 80% or more.

The bond magnet P _{1 according to} the first embodiment of the present invention described above is for the case where the pressure molding is the one-push molding from the upper punch 4, and the end surface on the side where the first layer P ₁₁ contacts the upper punch 4. Provided.

Bonded magnet P ₁ of the first embodiment described above is formed as shown in FIG. 4, for example. That is, the mold apparatus shown in FIG. 4 has a die 1 having a mold hole 1a that forms the outer periphery of the green compact, a core rod 2 that forms a hollow portion of the green compact, and a lower surface that forms the lower surface of the green compact. A punch 3 and an upper punch 4 that forms the upper surface of the green compact are provided.

Using such a mold apparatus, as shown in FIG. 4 (a-1), a cavity is formed by the mold hole 1a of the die 1, the core rod 2, and the lower punch 3, and powder such as a feeder 52 is supplied to the cavity. by means, the amount of resin fills the 0.5 to 1.0 wt% of the raw material powder _{M 2} (first filling step).

Then, as shown in FIG. 4 (a-2), and lowering the lower punch 3, a new cavity between the die hole 1a and the core rod 2 of the die 1 on the raw powder M ₂ filled in the previously formed as well as by feeder 51 to the cavity, the amount of resin fills the raw powder _{M 1} of 1.5 to 2.0 wt% (second filling process). By thus filling the raw material powder, a raw powder _{M 1} resin amount of 0.5 to 1.0% by weight in the cavity, the resin amount of 1.5 to 2.0 mass% raw powder _{M 1} Can be laminated.

Then, as shown in FIG. 4 (b), lowering the upper punch 4, by compression molding at a molding pressure 1470~2450MPa the raw powder _{M 1} and _{M 2} which are stacked filled into the cavity by the upper punch 4 pressure and the powder _{C 1} (compression molding step). At this time, the raw material powder _{M 1} and _{M 2} are molded integrally.

After the raw material powder is compression-molded as described above, as shown in FIG. 4 (c), the upper punch 4 is moved upward to return to the standby position, and the lower punch 3 is raised to raise the green compact C. ₁ is extruded from the mold hole 1a of the die 1 (extrusion process). In the green compact C ₁ , a layer that becomes the first layer P ₁₁ is formed on the end face side that contacts the upper punch 4. Therefore, since it is possible to absorb the deformation of the core rod 2 upon unloading the pressure of the upper punch 4 is elastically restored, it is possible to push the powder compact C ₁ without generating cracks. The (heat treatment step) by the powder compact C ₁ is heated to a predetermined temperature to obtain a bonded magnet P ₁ of the present invention. Incidentally, the second layer _{P 12} and the first layer _{P 11} is a main body are integrated.

Raw powder M ₁ and M ₂ of the above, the filling depth is filled with adjusted so that the height d of the height h, and the first layer P ₁₁ of the second layer P _12. Here, the raw material powder M ₁ and M _2, from being compressed as the integral time, the compression ratio in both powder are equal. Therefore, the ratio of the filling depth of the raw material powder filling depth of M ₁ and the raw material powder M _2, filled with equal ratio of the height d of the height h and the first layer P ₁₁ of the desired second layer P ₁₂ do it. Therefore, the filling depth of the raw material powder M _1, as described above, so that 1~3mm after molding, also filling depth of the raw powder M _2, as described above, so that a 9mm or more after the molding adjust.

In the first embodiment, the position of the die 1 is fixed and the movement of the lower punch 3 is controlled. However, the lower punch 3 may be fixed and the position of the die 1 may be controlled. Moreover, although the raw material powder was pressurized with the upper punch 4, it may be pressurized with the lower punch 3, and in that case, the order of filling the raw material powders M ₁ and M ₂ is changed and the raw material powder is directly pressurized. on the side of the punch, may be filled as the raw material powder M ₁ is small amounts of many magnetic powder resin amount is located.

(2) Second Embodiment The bonded magnet according to the first embodiment of the present invention and the first bonded magnet molding method according to the present invention described above are forms in which one-side press molding is performed. In many cases, the double-push molding in which the raw material powder is compression-molded by both the upper punch and the lower punch. That is, in the one-push molding, there is an advantage that the mold configuration is simple and easy to control, but the pressure for compressing the raw material powder is applied only from one punch, and this pressure is applied to the other punch while being attenuated through the raw material powder. Propagating and the reaction force of this pressure becomes the pressing force of the other punch. Therefore, the other end face is difficult to be densified with respect to the end face directly pressed. On the other hand, if pressure is directly applied to the raw material powder from both the upper punch and the lower punch, both end surfaces are densified, and the density of the bond magnet can be easily increased. However, in the case of double-press molding, the core rod is elastically deformed also on the lower punch side, so that cracks are likely to occur near the lower end surface.

The bonded magnet according to the second embodiment of the present invention corresponds to the above-described double pressing, and as shown in FIG. 5, the resin amount is 1.5-2. The first layer P ₂₁ and the third layer P _{23 of} 0% by mass are provided, and the second layer P ₂₂ having a resin amount of 0.5 to 1.0% by mass is configured as the main body in the remaining part. That is, bonded magnets P ₂ of the second embodiment of the present invention, also the lower punch 3 side, the amount of many magnetic powder resin amount are arranged fewer layers, cracking of the lower punch 3 side at the time of compression molding Is prevented from occurring.

Bond magnet P ₂ of the second embodiment of the present invention is molded in the manner of Figure 6, for example. The mold apparatus is the same as that used in the manufacturing method of the bonded magnet of the first embodiment. However, in the manufacturing method of the bonded magnet of the first embodiment described above, the die fixing is described. However, in the present embodiment, a case where a general withdrawal method (lower punch fixing) is applied in powder molding will be described. .

First, as shown in FIG. 6 (a-1), a cavity is formed by the die hole 1a of the die 1, the core rod 2 and the lower punch 3, and the feeder 53 is used for the resin. amount to fill the raw powder _{M 3} of 1.5 to 2.0 wt% (first filling step).

Then, as shown in FIG. 6 (a-2), raising the die 1, newly forms a cavity in the die hole 1a and the core rod 2 of the die 1 on the raw powder M ₃ filled previously together, the feeder 52 into the cavity, the amount of resin fills the 0.5 to 1.0 wt% of the raw material powder _{M 2} (second filling process).

Thereafter, further, as shown in FIG. 6 (a-3), to further increase the die 1, with a die hole 1a and the core rod 2 of the die 1 on the raw powder M ₂ filled just before, again newly to form a cavity, the feeder 51 into the cavity, the amount of resin fills the raw powder _{M 1} of 1.5 to 2.0 wt% (3 filling step). The resin and magnet powder used in the raw material powders M _{1 to} M ₃ may be the same or different.

By filling the raw material powder in this way, the raw material powders are stacked in the order of the raw material powder M ₃ , the raw material powder M ₂ , and the raw material powder M ₁ from the bottom in the cavity, and the amount of resin is large and the amount of magnet powder is small. The raw material powders M ₁ and M ₃ can be laminated and filled with the raw material powder M ₂ having a small amount of resin and a large amount of magnet powder in the middle at both ends.

Then, as shown in FIG. 6B, the upper punch 4 is lowered and the die 1 is lowered, and the raw material powder in the cavity is compression molded by the upper punch 4 and the lower punch 3 at a molding pressure of 1470 to 2450 MPa. To obtain a green compact C ₂ (compression molding process). That is, in this embodiment, the lower punch 3 is relatively lifted by lowering the die 1, and the raw material powder is pressed from both the upper punch 4 and the lower punch 3 to form a double press molding. . At this time, the raw material powders M ₁ and M ₃ are integrally formed at both ends, and the raw material powder M ₂ is integrally formed as a main body.

After compression molding the raw material powder as described above, the upper punch 4 is moved upward to return to the standby position as shown in FIG. until it coincides with the 3 upper end surface of is lowered to push the green compact C ₂ from the mold hole 1a of the die 1 (extrusion process). In the green compact C ₂ , layers that become the first layer P ₂₁ and the third layer P ₂₃ are formed on the end surfaces in contact with the upper punch 4 and the lower punch 3. Therefore, since it is possible to absorb the deformation of the core rod of the pressure of the upper punch 4 and the lower punch 3 upon unloading 2 is elastically restored, it is possible to push the green compact C ₂ without generating cracks. By heating the green compact C ₂ to a predetermined temperature, it is possible to obtain a bonded magnet P ₂ of the present invention. The first layer P ₂₁ and the third layer P ₂₃ are disposed at both end portions, and the second layer P ₂₂ is disposed at the intermediate portion and formed integrally.

In the second method for fabricating a bonded magnet of the present invention described above, the raw material powder M ₂ and the filling depth of the raw powder M _1, M ₃ are disposed at both ends of the first method for manufacturing a bonded magnet of the present invention You can set as well. The molding pressure may be set in the same manner as in the first method for manufacturing a bonded magnet of the present invention. In the second embodiment, the width method is used and the position of the lower punch 3 is fixed and the die 1 is controlled to move. However, the die 1 is fixed and the position of the lower punch 3 is controlled. It may be.

  The resin-coated magnet powder is prepared by, for example, kneading a solution obtained by dissolving a resin in an organic solvent into the magnet powder, and heating the magnet powder kneaded with the resin solution as necessary to volatilize the organic solvent component. Obtainable. That is, the resin solution mixed with the magnet powder wets and covers the surface of the magnet powder. From this state, the organic solvent component in the solution is volatilized and removed, so that only the resin component is the magnet powder. It remains as a film on the surface.

[First embodiment]
A Ti-containing nanocomposite magnet powder obtained by pulverizing and heat-treating a quenched alloy ribbon having a composition of Nd _8.6 Pr _0.1 Fe _84.4 B _6.0 Ti _0.9 atomic% obtained by the melt spinning method Prepared. The adjustment prepared bisphenol A type epoxy resin and a curing agent, and kneading by changing the addition amount of the magnetic powder and the resin in the proportions shown in Table 1, the raw material powder M ₂ forming the second layer P ₁₂ after the molding as well as, the magnet powder was added and mixed 1.5 wt% resin, to prepare a raw powder M ₁ for forming the first layer P ₁₁ after molding.

Using a raw material powder _{M 1} and _{M 2,} which was prepared as described above, on the filled raw material powder _{M 2} as filling depth 21.6 mm, the raw powder _{M 1} stacked filled as the filling depth 2.4 mm, One-press molding with an upper punch was performed at a molding pressure of 1960 MPa. And the outer diameter is 25 mm, the inner diameter is 17 mm, the height is 12 mm, the height of the second layer P ₁₂ formed by the raw material powder M ₂ is 10.8 mm, and the first layer P ₁₁ is formed by the raw material powder M ₁ . A cylindrical green compact having a height of 1.2 mm was molded to produce green compact samples of sample numbers 01 to 06.

  About these green compact samples, the inside diameter upper part of the green compact was observed visually, and the presence or absence of cracks was investigated. Further, a green compact sample in which no cracks were observed was heated in a nitrogen gas atmosphere at 180 ° C. for 2 hours for heat treatment, and then the density as a bonded magnet was measured by the Archimedes method. These results are also shown in Table 1.

From Table 1, in Sample No. 01 that the raw material powder M ₂ does not contain a resin, the raw material powder M ₂ is not harden, crack is generated in the green compact after extrusion. On the other hand, in the sample of the sample No. 02-06 using raw powder M ₂ containing resin 0.5 mass% or more, it encourages the magnet powder rearrangement resin giving sliding the magnet powder, the resin magnet powder Since it was bound, it could be molded without generating cracks. Density is also in the scope resin amount of the raw material powder _{M 2} is 0.5 to 2.0 mass%, the amount of resin is the highest density of the sample of 0.5% by weight of the sample No. 02, with an increase of the resin weight Shows a tendency to decrease. Then, Sample No. 05,06 weight resin of the raw material powder _{M 2} exceeds 1.0 weight%, the density is low below the 6.4 mg / ^{m 3.}

From the above, by incorporating a resin as a raw material powder M ₂ for forming the second layer P _12, by the range and the resin amount of 0.5 to 1.0 mass%, without causing cracks, It was confirmed that a high-density bonded magnet having a density of 6.4 Mg / m ³ or more can be obtained.

[Second Embodiment]
Using the same magnet powder and the resin to the first embodiment, the magnet powder, together with the addition of 0.5 wt% resin kneaded, to adjust the raw powder M ₂ forming the second layer P ₁₂ after molding, the table and kneading by changing the addition amount of the magnetic powder and the resin powder in the ratio shown in 2, to prepare a raw powder M ₁ for forming the first layer P _11.

  Using these raw material powders, cylindrical green compacts were molded in the same manner as in the first example, and green compact samples of sample numbers 07 to 11 were produced. These green compact samples were investigated for cracks in the same manner as in the first example, and after the heat treatment was performed on the green compact samples in which no cracks were observed in the same manner as in the first example, The density as a magnet was measured. These results are also shown in Table 2. Table 2 also shows the measured values of the sample No. 02 of the first example.

From Table 2, the sintered sample 07, 08 with the resin amount of the raw material powder M ₁ for forming the first layer P ₁₁ is less than 1.5 mass%, cracks occurred in the end portion of the green compact. On the other hand, in the sample of the sample No. 02,09～11 that the resin amount of the raw material powder M ₁ and 1.5 mass% or more, it was possible to obtain good green compact without cracks in the end. Density is also in the scope resin amount of 1.5 to 2.5 mass% of the raw material powder _{M 1,} the amount of resin is the highest density of the sample of 1.5 wt% of Sample No. 02, with an increase of the resin weight Shows a tendency to decrease. The density in the sample of the sample No. 11 in which the resin amount of the raw material powder _M in ₁ exceeds 2.0 mass% is lower below the 6.4 mg / ^{m 3.}

From the above, by incorporating a resin as a raw material powder M ₁ for forming the first layer P _11, that the range of this resin amount of 1.5 to 2.0 mass%, without causing cracks, It was confirmed that a high-density bonded magnet having a density of 6.4 Mg / m ³ or more can be obtained.

[Third embodiment]
Using the same magnet powder and the resin to the first embodiment, the magnet powder, and the addition of 0.5 wt% resin kneaded, with adjusting the raw material powder M ₂ for forming the second layer P _12, the magnet powder , it was added 1.5 wt% resin powder kneaded, to prepare a raw powder _{M 1} for forming the first layer _{P 11.}

By using these raw powders, as shown in Table 3, were filled with different filling depth of the raw material powder M ₁ and M _2, other molding conditions Sample No. molded in the same manner as in the first embodiment 12 to 16 green compact samples were prepared. These green compact samples were examined for cracks in the same manner as in the first example, and cracks were investigated, and the green compact samples in which no cracks were observed were heat treated in the same manner as in the first example. Then, the density as a bonded magnet was measured. These results are also shown in Table 3. Table 3 also shows the measured values of the sample No. 02 of the first example.

From Table 3, samples of sample numbers 12 only raw powder M ₂ forming the second layer P ₁₂ is a body (without the first layer P _11), the cracks occurred in the end portion of the green compact. On the other hand, in the sample of the sample No. 02,13～16 the filling depth of the raw material powder _{M 1} and the height of the first layer _{P 11} and above 1.0mm as above 2.0mm for forming the first layer _{P 11,} A good green compact could be obtained without cracking at the end. Further, in the height range of 1.0~3.0mm of the first layer _{P 11,} the density of the sample of the sample No. 13 height 1.0mm of the first layer _{P 11} is the highest, the first layer P _As the height of ₁₁ increases, the density tends to decrease. Then, in the sample of the sample No. 16 in which the height of the first layer _{P 11} exceeds 3mm density is lower below the 6.4 mg / ^{m 3.}

From the above, it provided with a first layer _{P 11} on the end portion of the second layer _{P 12,} by the height of the first layer _{P 11} in the range of 1.0 to 3.0 mm, to generate cracks It was confirmed that a high-density bonded magnet having a density of 6.4 Mg / m ³ or more can be obtained.

[Fourth embodiment]
Using the same magnet powder and the resin to the first embodiment, the magnet powder, and the addition of 0.5 wt% resin kneaded, with adjusting the raw material powder M ₂ forming the second layer P ₁₂ is a main body, the magnet powder, and the addition of 1.5 wt% resin kneaded to prepare a raw powder M ₁ for forming the first layer P _11.

  Using these raw material powders, as shown in Table 4, the molding pressure was changed and the other molding conditions were molded in the same manner as in the first example to prepare green compact samples of sample numbers 17-22. These green compact samples were examined for cracks in the same manner as in the first example, and cracks were investigated, and the green compact samples in which no cracks were observed were heat treated in the same manner as in the first example. Then, the density as a bonded magnet was measured. These results are also shown in Table 4. Table 4 also shows the measured values of the sample No. 02 of the first example.

From Table 4, the density of sample No. 17 having a molding pressure of less than 1470 MPa was lower than 6.4 Mg / m ³ . On the other hand, in the samples Nos. 02 and 18-21 having a molding pressure of 1470 to 2450 MPa, the density was a high value exceeding 6.4 Mg / m ³ . As the molding pressure increases, the density increases. However, when the molding pressure exceeds 1960 MPa, the rate of increase in density decreases with respect to the increase in molding pressure. And in the sample of the sample number 22 whose molding pressure exceeds 2450 MPa, the molding pressure is excessive and cracks are generated in the green compact.

From the above, it was confirmed that a high-density bonded magnet having a density of 6.4 Mg / m ³ or more can be obtained without generating cracks in a molding pressure range of 1470 to 2450 MPa.

The bonded magnet of the present invention has a high magnetic flux density and a maximum energy product (BH) _max by obtaining a high density, and can contribute to miniaturization and weight reduction of equipment, and can be used for various small motors and sensors. Can be used in a wide range of fields such as general household appliances, automobile parts, acoustic equipment, medical equipment, general industrial equipment.

1 ... die, 1a ... die hole, 2 ... core rod, 3 ... lower punch, 31 ... eject pin, 4 ... upper punch, 5,51,52,53 ... feeder, M ... raw powder, M 1 _... first raw material powder M ₂ ... second raw material powder, M ₃ ... third raw material powder, C, C ₁ , C ₂ ... green compact, P ₁ , P ₂ ... bond magnet, P ₁₁ , P ₂₁ ... first layer, P ₁₂ , P ₂₂ ... second layer, P ₂₃ ... third layer, d ... height of the first layer and the third layer, h ... height of the second layer, H ... height of the green compact.

Claims (9)

A bonded magnet obtained by binding magnet powder with a resin, having a cylindrical shape having a hollow portion, and a resin amount of 1.5 to 2.0 mass at both ends or one end in the axial direction of the hollow portion % Of the first layer is provided, and the remainder is provided with the second layer having a resin amount of 0.5 to 1.0% by mass, and the density is 6.4 Mg / m ³ or more. Bond magnet.   The bonded magnet according to claim 1, wherein the first layer has an axial height of 1 to 3 mm.   The bonded magnet according to claim 1 or 2, wherein the second layer has an axial height of 9 mm or more. Using a die device comprising a die having a mold hole, a core rod, and an upper punch and a lower punch that are slidably fitted to the core rod and the mold hole,
A first filling that fills a cavity formed by the die hole of the die, the core rod, and the lower punch with a second raw material powder containing a magnet powder having a resin addition amount of 0.5 to 1.0 mass%. Process,
On the second raw material powder, a second filling step of filling and laminating the first raw material powder containing a magnet powder having a resin addition amount of 1.5 to 2.0% by mass;
A compression molding step in which the first and second raw material powders are compression-molded by one-press molding at a molding pressure of 1470 to 2450 MPa by the upper punch;
An extrusion process for extruding the obtained green compact;
A method of manufacturing a bonded magnet, comprising performing a heat treatment step of heating the green compact and binding the magnet powder with a resin. Using a die device comprising a die having a mold hole, a core rod, and an upper punch and a lower punch that are slidably fitted to the core rod and the mold hole,
A first filling that fills a cavity formed by the die hole of the die, the core rod, and the lower punch with a third raw material powder containing a magnet powder having a resin addition amount of 1.5 to 2.0 mass%. Process,
A second filling step of filling and laminating a second raw material powder containing a magnet powder having a resin addition amount of 0.5 to 1.0% by mass on the third raw material powder;
A third filling step of filling and laminating the first raw material powder containing the magnet powder having a resin addition amount of 1.5 to 2.0% by mass on the second raw material powder;
A compression molding process in which the first, second, and third raw material powders are compression-molded by double-press molding at a molding pressure of 1470 to 2450 MPa by the upper punch and the lower punch;
An extrusion process for extruding the obtained green compact;
A method of manufacturing a bonded magnet, comprising performing a heat treatment step of heating the green compact and binding the magnet powder with a resin.   6. The method of manufacturing a bonded magnet according to claim 4, wherein a filling depth of the first raw material powder is a depth of 1 to 3 mm after compression molding.   The method for producing a bonded magnet according to claim 5, wherein the filling depth of the third raw material powder is a depth of 1 to 3 mm after compression molding.   The method for manufacturing a bonded magnet according to any one of claims 4 to 7, wherein a filling depth of the second raw material powder is a depth of 9 mm or more after compression molding.   The method for producing a bonded magnet according to any one of claims 4 to 8, wherein the first to third raw material powders are made of resin-coated magnet powder obtained by coating a surface of a magnet powder with resin.

Images