JP2018125517A - Shaft-integrated bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shaft-integrated bonded magnet capable of achieving reductions in weight and cost while maintaining sufficient magnetic characteristics, by radially changing the density of a bonded magnet.SOLUTION: In a shaft-integrated bonded magnet 1 including a cylindrical bonded magnet 3 integrally provided on a peripheral surface of a columnar shaft 2, the density on an outer peripheral side of the bonded magnet 3 (density of an outer peripheral side portion 3a) is greater than the density on an inner peripheral side (density of an inner peripheral side portion 3b). In the shaft 2, a central portion 2a in a shaft length direction has a larger diameter than both end portions (one end portion 2b and the other end portion 2c), and the bonded magnet 3 is integrally provided to cover the whole area of the central portion 2a of the shaft 2 and a partial area of both end portions (one end portion 2b and the other end portion 2c) on a central portion 2a side.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a shaft-integrated bonded magnet used for various motors.

  A bonded magnet formed by solidifying and molding magnetic powder and a resin as a binder of the magnetic powder has advantages of higher dimensional accuracy and higher degree of freedom of shape than a sintered magnet. A shaft-integrated bond magnet obtained by inserting a shaft serving as a rotor shaft into such a cylindrical bonded magnet is used for various motors in electronic devices, cameras, automobiles, and the like.

  Such a shaft-integrated bonded magnet and a manufacturing method thereof are disclosed in Patent Document 1. In Patent Document 1, a support member made of a rotor yoke in which a rotor shaft is inserted is disposed in a mold of a compression molding apparatus, and Nd—Fe—B magnetic powder and epoxy resin are formed around the support member. There is described a shaft-integrated bonded magnet obtained by supplying a magnetic composition obtained and press-molding.

  According to Patent Document 1, it is possible to provide a shaft-integrated bonded magnet in which the weight ratio and volume ratio of the magnetic powder in the magnetic composition obtained by mixing the magnetic powder and the binder are increased. Therefore, it is possible to reduce the size and performance of the motor.

JP-A-6-140235

  In the conventional shaft-integrated bonded magnet including Patent Document 1, since the density is uniformly formed throughout the bonded magnet, the magnetic powder in a portion that does not effectively act on the external magnetic flux when incorporated in the motor. There is a problem of being wasted.

  The present invention has been made in view of such circumstances, and by changing the density in the radial direction of the bonded magnet, a shaft-integrated type that can achieve weight reduction and cost reduction while maintaining sufficient magnetic properties. An object is to provide a bonded magnet.

  The shaft-integrated bond magnet according to the present invention is a shaft-integrated bond magnet in which a cylindrical bond magnet is integrally provided on a peripheral surface of a columnar shaft, and the density on the outer peripheral side of the bond magnet is It is characterized by being larger than the density on the inner peripheral side of the bonded magnet.

  In the present invention, there is a difference in density between the inner peripheral side (shaft side) and the outer peripheral side of the bonded magnet, and the density on the outer peripheral side is larger than the density on the inner peripheral side. Increase the density on the outer peripheral side that works effectively on the external magnetic flux when incorporated in the motor to increase the amount of magnetic powder per unit volume, and increase the density on the inner peripheral side that does not work effectively on the external magnetic flux. The volume is reduced to reduce the amount of magnetic powder per unit volume. Therefore, sufficient magnetic characteristics can be obtained even if the whole is lightened.

  In the shaft-integrated bond magnet according to the present invention, the density of the region from the outer periphery of the bond magnet to at least 2 mm in the direction perpendicular to the length direction of the shaft is defined as the density on the outer periphery side of the bond magnet. The inner circumference of the bond magnet is defined as the density of the inner circumference side of the bond magnet, with the density of the region from the thickest outer diameter to the bond magnet in the direction perpendicular to the length direction of the shaft being at least 2 mm. The density difference between the side and the outer peripheral side is 2% or more and 5% or less.

  The shaft-integrated bonded magnet according to the present invention is characterized in that a density difference between the inner peripheral side and the outer peripheral side of the bonded magnet is 2% or more and 3% or less.

  If the density difference is too small, the effect of weight reduction cannot be obtained. On the other hand, when the density difference is too large, there is a possibility that the magnetic characteristics are deteriorated due to the influence (distortion, crack, etc.) of the density difference at the boundary portion. Therefore, in the present invention, the density difference between the inner peripheral side and the outer peripheral side of the bonded magnet is set to 2% or more and 5% or less to achieve both reduction in weight and maintenance of sufficient magnetic properties. In order to realize this compatibility, the density difference is more preferably 2% or more and 3% or less.

  The shaft-integrated bonded magnet according to the present invention is characterized in that the bonded magnet includes a magnetic powder and an anaerobic resin.

  In the present invention, the bonded magnet has magnetic powder and anaerobic resin. Therefore, since excess anaerobic resin that has come into contact with air can be easily removed by washing or the like, the filling rate of the magnetic powder can be increased with high strength.

  In the shaft-integrated bonded magnet according to the present invention, the shaft has a central portion in the axial length direction having a larger diameter than both end portions, and the whole region of the central portion of the shaft and a part of the both end portions on the central portion side. The bonded magnet is integrally provided so as to cover the region.

  In the present invention, a cylindrical shaft whose central portion in the axial length direction has a diameter larger than both end portions is covered with a cylindrical shape covering the entire region of the central portion of the shaft and a partial region on the central portion side of both end portions. The bonded magnet is integrally provided. Therefore, the coupling force between the shaft and the bond magnet is high, and the axial pull-out strength between the shaft and the bond magnet is excellent.

  According to the shaft-integrated bonded magnet of the present invention, even if the density of the entire shaft-integrated bonded magnet is low, only the density of the portion that contributes to the motor characteristics can be selectively increased. It is possible to achieve weight reduction and cost reduction while maintaining a good magnetic property.

It is a perspective view which shows the shaft integrated bond magnet which concerns on this invention. It is sectional drawing which shows the shaft integrated bond magnet of 1st Embodiment. It is sectional drawing which shows the shaft integrated bond magnet of 2nd Embodiment. It is sectional drawing which shows the procedure of the manufacturing process of the shaft integrated bond magnet of 2nd Embodiment. It is sectional drawing which shows the procedure of the manufacturing process of the shaft integrated bond magnet of 2nd Embodiment. It is sectional drawing which shows the procedure of the manufacturing process of the shaft integrated bond magnet of 2nd Embodiment. It is a graph which shows the relationship between a shaping | molding pressure and a molded object density.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.

  FIG. 1 is a perspective view showing a shaft-integrated bonded magnet according to the present invention. The shaft-integrated bond magnet 1 is configured by integrating a columnar shaft 2 and a cylindrical bond magnet 3. Due to the difference in the shape of the shaft 2, the first embodiment and the second embodiment exist.

  FIG. 2 is a cross-sectional view illustrating the shaft-integrated bonded magnet 1 according to the first embodiment. The shaft 2 in the shaft-integrated bonded magnet 1 according to the first embodiment has a cylindrical shape with the same diameter throughout. The bond magnet 3 is integrally provided so as to cover the outer peripheral surface of the central portion in the axial length direction of the shaft 2.

  In the shaft-integrated bond magnet 1 of the first embodiment, for example, the length and diameter of the shaft 2 are 55 mm and 4 mm, respectively, and the length and outer diameter of the bond magnet 3 are 18 mm and 20 mm, respectively. This dimension is merely an example, and the length and diameter of the shaft 2 and the length and outer diameter of the bond magnet 3 may be set as appropriate according to the required specifications.

  FIG. 3 is a cross-sectional view showing the shaft-integrated bonded magnet 1 according to the second embodiment. The shaft 2 of the shaft-integrated bonded magnet 1 according to the second embodiment has a columnar shape as a whole, but the central portion 2a in the axial length direction has a larger diameter than both ends. The bonded magnet is configured to cover the outer peripheral surface of the entire area of the thick central portion 2a of the shaft 2 and the outer peripheral surface of a part of the both end portions (one end portion 2b and the other end portion 2c) on the central portion 2a side. 3 is provided integrally.

  In the shaft-integrated bonded magnet 1 of the second embodiment, for example, the length of the shaft 2, the diameter of the central portion 2a, and the diameters of both end portions (one end portion 2b and the other end portion 2c) are 55 mm and 7 mm, respectively. The length and outer diameter of the bonded magnet 3 are 18 mm and 20 mm, respectively. Further, for example, the lengths of L1, L2, L3, L4, L5, and L6 in FIG. 3 are 18 mm, 20 mm, 2 mm, 14 mm, 2 mm, and 17 mm, respectively. This dimension is merely an example, and the length and diameter of the shaft 2, the length and outer diameter of the bonded magnet 3, and the lengths L1 to L6 of each part may be appropriately set according to necessary specifications. good.

  As a material of the shaft 2, a laminated body of silicon steel plates, an aluminum alloy, stainless steel, or the like can be used, and a resin or a composite material of a resin and a metal powder or an alloy powder may be used. Further, the shaft 2 is not limited to a columnar shape but may be a prismatic shape. Furthermore, a groove may be provided on the surface in contact with the bond magnet 3 in order to enhance the anti-slip effect.

  As the magnetic powder of the bond magnet 3, rare earth magnetic powder, ferrite magnetic powder or the like can be used. As the rare earth magnetic powder, an R-T-B magnetic powder (R is at least one kind of rare earth element and must contain at least one of Nd and Pr, T is Fe or Fe and Co, and B is boron. R-TN-based magnetic powder (R is at least one kind of rare earth element and must contain Sm, T is an iron group element, N is nitrogen), etc. Is given. The shape of the RTB-based magnetic powder is preferably a flat shape (for example, the shape aspect ratio of the powder particles = the minor axis / the major axis is 0.3 or less). By using the R-T-B magnetic powder having a flat shape, the magnetic powder can be easily laminated when the material (mixture of magnetic powder and resin) is compression-molded. Further, it becomes difficult to form voids or resin pools between the magnetic powders during molding, and high-density filling becomes possible. The average particle size of the RTB-based magnetic powder is preferably 20 μm or more and 300 μm or less, more preferably 40 μm or more and 250 μm or less. Here, the average particle diameter is the arithmetic average diameter of the volume distribution, and is measured using a laser diffraction particle size distribution measuring device.

  On the other hand, the resin used for the bond magnet 3 is a thermosetting resin used for a general bond magnet, and preferable resins include, for example, an epoxy resin, a phenol resin, and a polyimide resin.

  In the shaft-integrated bonded magnet 1 according to the present invention having such a configuration, a cylinder integrally provided on the peripheral surface of the shaft 2 in any of the first embodiment and the second embodiment. There is a difference in density between the inner peripheral side and the outer peripheral side of the bonded magnet 3, and the density of the outer peripheral side portion 3a is larger than the density of the inner peripheral side portion 3b. The bond magnet 3 is formed by compression molding a mixture of magnetic powder and resin (magnetic composition: compound) as a material, and the difference in density is defined by the ratio of voids. That is, the void ratio in the outer peripheral portion 3a is smaller than the void ratio in the inner peripheral portion 3b, and the mixing ratio of the magnetic powder and the resin is the same in the outer peripheral portion 3a and the inner peripheral portion 3b. is there.

  The density difference between the outer peripheral side portion 3a and the inner peripheral side portion 3b of the bond magnet 3 is 2% or more and 5% or less, more preferably 2% or more and 3% or less. When the density difference is less than 2%, the weight reduction that is the effect of the present invention cannot be achieved. On the other hand, when the density difference exceeds 5%, it is considered that the magnetic characteristics are deteriorated due to the influence (distortion, cracking, etc.) of the density difference at the boundary portion. Therefore, in order to achieve weight reduction while maintaining sufficient magnetic characteristics when incorporated in a motor, the density difference is set to 2% or more and 5% or less. Here, the density of the outer peripheral side portion 3 a of the bond magnet 3 is a density in a region from the outer periphery of the bond magnet 3 to at least 2 mm in a direction perpendicular to the length direction of the shaft 2. The density of the side portion 3 b refers to the density of the region from the thickest outer diameter of the shaft 2 to at least 2 mm toward the bonded magnet 3. The density is measured by using the Archimedes method after cutting the bonded magnet and cutting it out.

Specifically, as an example, the density of the outer peripheral side portion 3a is 5.5 to 6.5 g / cm ³ , and the density of the inner peripheral side portion 3b is 5.4 to 6.5 g / cm ^3. The density of the side portion 3a is 5.8 to 6.2 g / cm ³ , and the density of the inner peripheral side portion 3b is 5.6 to 6.0 g / cm ³ .

  In the shaft-integrated bonded magnet 1 of the present invention, there is a difference in density between the inner peripheral side (the shaft 2 side) and the outer peripheral side of the bond magnet 3, and the density of the outer peripheral side portion 3a of the bond magnet 3 is the inner peripheral side portion 3b. It is larger than the density. Increase the density on the outer peripheral side that works effectively on the external magnetic flux when incorporated in the motor to increase the amount of magnetic powder per unit volume, and increase the density on the inner peripheral side that does not work effectively on the external magnetic flux. The volume is reduced to reduce the amount of magnetic powder per unit volume. Therefore, it is possible to obtain sufficient magnetic characteristics even if the whole is lightened.

  Unlike the first embodiment in which the diameter of the shaft 2 is the same over the entire region in the axial length direction, in the second embodiment, the diameter of the central portion 2a in the axial length direction of the shaft 2 is set to both end portions (one end portion 2b and others). It is thicker than the diameter of the end 2c). Therefore, in the second embodiment, the coupling force between the shaft 2 and the bond magnet 3 is higher than that in the first embodiment, and the shaft 2 and the bond magnet 3 are disconnected in the axial direction. Excellent strength.

  Hereinafter, specific dimensions and densities of the outer peripheral side portion 3a and the inner peripheral side portion 3b having such a difference in density will be described using the first embodiment as an example. In the following, as shown in FIG. 2, D1 represents the outer diameter (mm) of the outer peripheral portion 3a, and D2 represents the outer diameter (mm) of the inner peripheral portion 3b.

Table 1 shows an example of the present invention (No. 2, 4, 6) when the outer diameter D1 of the outer peripheral portion 3a is 20 mm. The diameter of the shaft 2 was 2 mm. As the number of magnetic poles increases, a magnetic path is not formed to the inside, so that sufficient magnetic characteristics can be obtained even if the inner peripheral side portion 3b having a reduced density is enlarged. Table 1 also shows examples of shaft-integrated bonded magnets (Nos. 1, 3, and 5) as comparative examples in which the density of the bonded magnet is uniform over the entire region. Examples of the present invention and comparative examples are made of materials (consisting of magnetic powder and resin. Magnetic powder is R-T-B magnetic powder and resin is epoxy resin. R-T-B magnetic powder is MQP-14. -9 (manufactured by Polycorp) was used, and the composition of MQP-14-9 was 16.7 mass% Nd, 3.8 mass% La, 5.5 mass% Pr, 1.0 mass. % Of B and the balance Fe, and MQP-14-9 has an average particle size of 100 μm, and the resin is 2% by mass of the whole material.), Shape and size are the same. The amount of magnetic flux by the flux meter was measured by connecting a Helmholtz type coil to a Lake Shore flux meter manufactured by Toyo Technica. For example, No. of the present invention example. 2, the number of magnetic poles is 4, the outer diameter D1 of the outer peripheral portion 3a is 20 mm, the density is 6.1 g / cm ³ , the outer diameter D2 of the inner peripheral portion 3b is 7 mm, and the density is 5.9 g / cm ^3. The density difference is 0.2 g / cm ³ (3%) and the total weight is 33.1 g. No. No. 2 of the comparative example corresponding to 1, the number of magnetic poles is 4, the outer diameter D1 of the bonded magnet is 20 mm, the density is uniform 6.1 g / cm ³ , and the overall weight is 33.2 g. No. 1 and no. When 2 is compared, a weight reduction of 0.1 g can be achieved.

  Table 2 shows examples of the present invention (No. 8, 10, 12) when the outer diameter D1 of the outer peripheral portion 3a is 30 mm, and comparative examples (No. 7, 9, 11) corresponding thereto. Is shown. The diameter of the shaft 2 was 5 mm.

  From the above, it can be seen that in the present invention example, the magnetic characteristics (the amount of magnetic flux by the flux meter) are only a slight decrease compared to the comparative example, the weight is reduced, and the cost is reduced.

  Next, a comparison between the shaft-integrated bonded magnet 1 according to the second embodiment (example of the present invention) and a comparative example (when there is no density difference in the entire bonded magnet) will be described. The magnetic powder and resin used for the bonded magnets in the comparative example and the inventive example were Nd—Fe—B based magnetic powder (magnetic powder of MQP-14-9 (manufactured by Polycorp)) having an average particle diameter of 100 μm and 2% by mass, respectively. It is an epoxy resin. The number of poles is 4, the shape is as shown in FIG. 3, and the dimensions are as described above.

In the comparative example, the density of the entire bonded magnet was uniform at 6.1 g / cm ³ , whereas in the inventive example, the outer peripheral side portion 3a (outer diameter 20 mm) and inner peripheral side portion 3b (outer diameter) of the bonded magnet were used. 7 mm) The respective densities were 6.1 g / cm ³ and 5.9 g / cm ³ . As a result, the weight of the comparative example was 31 g, whereas the weight of the present invention was 30 g, confirming that a weight reduction of about 3% was achieved. Therefore, in the example of the present invention, it can be seen that weight reduction can be achieved while maintaining sufficient magnetic characteristics.

  In the example of the present invention, the runout accuracy is as small as ± 15 μm, and the bond magnet does not come off or crack even when rotated at 65000 rpm, and the mechanical properties are excellent.

  Table 3 shows the characteristics when the difference in density between the outer peripheral side portion 3a and the inner peripheral side portion 3b is changed in the shaft-integrated bonded magnet 1 of the present invention (No. 14 to No. 18). ing. In Table 3, the characteristic when there is no density difference (No. 13) is also shown as a comparative example. The outer diameter D1 of the outer peripheral side portion 3a was 30 mm, the outer diameter D2 of the inner peripheral side portion 3b was 15 mm, and the diameter of the shaft 2 was 5 mm.

  No. in which the density difference is in the range of 2 to 5%. 14-No. As can be seen from FIG. 16, the weight can be reduced while maintaining sufficient magnetic properties.

On the other hand, No. having a density difference of 10%. In No. 18, although the weight reduction is remarkable, since the density of the inner peripheral side portion 3b is too low at 5.5 g / cm ³ , there is a possibility that a problem may occur in the strength of the bond magnet 3. In addition, No. having a density difference of 7%. In No. 17, the density of the inner peripheral side portion 3b is the minimum necessary 5.7 g / cm ³ in consideration of strength, but this is not preferable in consideration of a decrease in density due to variation in mass production. On the other hand, no. Of course, with 13 it is not possible to reduce the weight.

  From the above, the density difference is preferably 2% or more and 5% or less, and more preferably 2% or more and 3% or less when the magnetic characteristics and strength are realized at a high level.

  In each example shown in Table 3, there is no great difference in the amount of magnetic flux by the flux meter because the outer diameter D2 of the inner peripheral portion 3b is smaller than the outer diameter D1 of the outer peripheral portion 3a and the density is low. The thickness of the high portion is large and the number of magnetic poles is as large as eight. Therefore, it is considered that only the vicinity of the surface of the bond magnet 3 is magnetized.

  Hereinafter, the procedure for producing the shaft-integrated bonded magnet 1 according to the second embodiment of the present invention will be described with reference to FIGS. The shaft-integrated bonded magnet according to the first embodiment is different from the shaft-integrated bonded magnet according to the second embodiment in the shape of the shaft, but the manufacturing process of FIGS. 4 to 6 to be described later is the shaft according to the second embodiment. It is the same as an integrated bond magnet.

  FIG. 4A shows the start position (hereinafter referred to as “fixed position”) of the molding operation of the molding apparatus used in the manufacturing process. The molding apparatus includes a cylindrical die 10, an upper mold 20, and a lower mold 30.

  The upper die 20 has a long cylindrical first upper punch 21 having an outer diameter substantially equal to the inner diameter of the die 10 and a second long cylindrical shape having an outer diameter substantially equal to the inner diameter of the first upper punch 21. The triple structure includes an upper punch 22 and a long cylindrical upper core 23 having a diameter substantially equal to the inner diameter of the second upper punch 22, and can be inserted through the die 10 from above. The first upper punch 21 can be inserted vertically in the die 10, the second upper punch 22 can be inserted vertically in the first upper punch 21, and the upper core 23 is inserted in the second upper punch 22. Can be inserted vertically. The movement (up / down) of the first upper punch 21, the movement (up / down) of the second upper punch 22, and the movement (up / down) of the upper core 23 can be performed independently of each other.

  The lower mold 30 includes a long cylindrical first lower punch 31 having an outer diameter substantially equal to the inner diameter of the die 10 and a long cylindrical first punch having an outer diameter substantially equal to the inner diameter of the first lower punch 31. 2 A triple structure including a lower punch 32 and a long cylindrical lower core 33 having a diameter substantially equal to the inner diameter of the second lower punch 32, and can be inserted through the die 10 from below. The first lower punch 31 can be inserted vertically in the die 10, the second lower punch 32 can be inserted vertically in the first lower punch 31, and the lower core 33 is inserted in the second lower punch 32. Can be inserted vertically. The movement (up / down) of the first lower punch 31, the movement (up / down) of the second lower punch 32, and the movement (up / down) of the lower core 33 can be performed independently of each other.

  First, as shown in FIG. 4B, the first lower punch 31 is lowered to form a space 41 between the second lower punch 32 and the die 10. Next, as shown in FIG. 4C, the space 42 is filled with a material 42 (a mixture of magnetic powder and resin (magnetic composition)) of the bond magnet 3. The descending distance d1 (depth of the space 41) at this time is the length of the bond magnet 3 (the length L1 shown in FIG. 3) in the produced shaft-integrated bond magnet 1 and the material in the compression molding process described later. 42 is determined in consideration of the compression ratio of 42.

  Next, as shown in FIG. 4D, the lower core 33 is lowered to form an opening portion 43 inside the second lower punch 32. The descending distance d2 (the length of the open portion 43) at this time is determined in consideration of the length of the region of the one end portion 2b of the shaft 2 where the outer peripheral surface of the shaft-integrated bonded magnet 1 is not covered with the bonded magnet 3. The That is, it is determined in consideration of the lengths L5 and L6 shown in FIG. 3 and the compression rate.

  Next, as shown in FIG. 5A, a part of one end portion 2 b of the shaft 2 prepared in advance is inserted into the opening portion 43. At this time, the shaft 2 is lowered until one end surface of the one end portion 2 b of the shaft 2 comes into contact with the lower core 33. The shaft 2 may be lowered by its own weight, or may be lowered manually or using a dedicated jig (dedicated device).

  Next, as shown in FIG. 5B, the first upper punch 21, the second upper punch 22, and the upper core 23 are lowered. The upper core 23 is lowered until it comes into contact with one end surface of the other end 2 c of the shaft 2, and the shaft 2 is sandwiched between the upper core 23 and the lower core 33. Further, the first upper punch 21 and the second upper punch 22 are lowered to a position that covers a partial region of the other end 2 c of the shaft 2. The lowering positions of the first upper punch 21 and the second upper punch 22 are determined in consideration of the length of the region of the other end 2c of the shaft 2 whose outer peripheral surface is not covered with the bond magnet 3 in the shaft-integrated bonded magnet 1. Is done. That is, it is determined in consideration of the lengths L2 and L3 shown in FIG. 3 and the compression rate.

  4D to FIG. 5A, when the lower core 33 is lowered to form the opening portion 43 inside the second lower punch 32 in FIG. 4D, the lowering distance d2 (opening) The length of the portion 43) is equal to the length of the region of the one end 2b of the shaft 2 (length L6 shown in FIG. 3) and the outer peripheral surface of the shaft-integrated bonded magnet 1 whose outer peripheral surface is not covered with the bond magnet 3. It may be a length corresponding to the sum of the length of the region covered with the magnet 3 (length L5 shown in FIG. 3). At this time, in FIG. 5A, the whole end portion 2b of the shaft 2 is inserted into the open portion 43. As a result, the boundary between the one end portion 2b and the center portion 2a of the shaft 2 and the upper surface of the filled material 42 The upper surface of the second lower punch 32 and the upper surface of the die 10 are at the same position in the vertical direction.

  Next, as shown in FIG. 5C, the second lower punch 32, the upper core 23, and the lower core 33 are lowered in conjunction with each other. At this time, the first upper punch 21 and the second upper punch 22 are further lowered in conjunction with each other. Then, as shown in FIG. 5D, a part of the one end 2 b of the shaft 2, a part of the center 2 a and the other end 2 c are buried in the material 42. The descending distances of the upper core 23 and the lower core 33 and the first upper punch 21 and the second upper punch 22 at this time (positions of the upper core 23 and the lower core 33, the first upper punch 21 and the second upper punch 22 in FIG. 5B). 5D to the positions of the upper core 23 and the lower core 33 and the positions of the first upper punch 21 and the second upper punch 22 in FIG. 5D), the outer peripheral surfaces of the one end 2b and the other end 2c of the shaft 2 are bonded magnets 3. It is determined in consideration of the length of the area to be covered (lengths L3 and L5 shown in FIG. 3) and the compression ratio.

  As shown in FIG. 5D, the first upper punch 21 and the second upper punch 22 are lowered to contact the upper surface of the material 42 or to the upper surface of the die 10. As a result, the shaft 2 and the material 42 are sealed by the upper mold 20 and the lower mold 30.

  5B to 5D, when lowering the second lower punch 32, the second lower punch 32 is lowered to the lowered position of the first lower punch 31 (lowered by the lowering distance d1 shown in FIG. 4B). However, the lowering position of the second lower punch 32 may be positioned above or below the lowering position of the first lower punch 31 according to the shape of the shaft-integrated bond magnet 1 or the like.

  5B to FIG. 5D, the upper core 23 and the lower core 33 are interlocked while the shaft 2 is previously sandwiched between the upper core 23 and the lower core 33 and the second lower punch 32 is lowered. Then, instead of the step of burying a part of one end part 2b of the shaft 2 and a part of the central part 2a and the other end part 2c in the material 42, the shaft 2 is preliminarily formed by the upper core 23 and the lower core 33. Alternatively, the lower core 33 may be lowered while the second lower punch 32 is lowered, and the shaft 2 may be lowered by its own weight while the shaft 2 is placed on the lower core 33. The shaft 2 may be lowered manually or using a dedicated jig (dedicated device).

  Next, as shown in FIG. 6A, the die 10 and the first lower punch 31 are lowered, and the second upper punch 22 is lowered. As the die 10 and the first lower punch 31 are lowered, the second lower punch 32 is relatively raised.

  6B, the die 10 is lowered, and the upper core 23, the lower core 33, the first upper punch 21 and the second upper punch 22 are lowered while the shaft 2 is sandwiched between the upper core 23 and the lower core 33. Let Here, the lowering amounts of the first upper punch 21 and the second upper punch 22 are adjusted so that the height positions of the surfaces of the first upper punch 21 and the second upper punch 22 in contact with the material 42 are the same. Further, the rising amounts of the first lower punch 31 and the second lower punch 32 are adjusted so that the height positions of the surfaces of the first lower punch 31 and the second lower punch 32 in contact with the material 42 are the same. As the die 10 is lowered, the first lower punch 31 and the second lower punch 32 are relatively raised. Then, the material 42 is compressed from the two directions of the lower direction and the upper direction by the first upper punch 21 and the second upper punch 22, and the first lower punch 31 and the second lower punch 32, so that the shaft 2 and the material 42 are compressed. Are integrally molded.

  Although the die 10 is lowered, the first lower punch 31 and the second lower punch 32 may be directly raised. 6A and 6B, the lowering distance of the die 10 and the lowering distances of the upper core 23 and the lower core 33 may be the same or different. The lowering distance of the die 10, the upper core 23 and the lower core 33, the first upper punch 21 and the second upper punch 22, or the rising distance when the first lower punch 31 and the second lower punch 32 are raised will be described later. It may be determined in consideration of the shape of the molded product 44 and the like.

  Next, as shown in FIG. 6C, the die 10, the first upper punch 21, the second upper punch 22, the upper core 23, the first lower punch 31, the second lower punch 32, and the lower core 33 are all raised. At this time, the ascending operation is performed until the die 10, the first lower punch 31, and the second lower punch 32 return to their home positions. Next, as shown in FIG. 6D, the first upper punch 21, the second upper punch 22, and the upper core 23 are further raised and returned to their home positions. Thereafter, the molded product 44 is removed from the die 10 and the molding process is terminated. 6A to 6D, instead of lowering only the die 10 and taking out the molded product 44 from the die 10, the die 10, the first upper punch 21, the second upper punch 22, All of the upper core 23, the first lower punch 31, the second lower punch 32, and the lower core 33 may be operated so as to return to their home positions.

  The taken-out molded product 44 is heat-treated at 200 ° C. for 1 hour to cure the resin. Thereby, the shaft-integrated bonded magnet 1 having a desired density and shape is obtained.

  In the molding process described above, as shown in FIG. 5C, the second lower punch 32, which has the same height as the upper surface of the die 10, is moved down in conjunction with the second lower punch 32, the upper core 23, and the lower core 33. Descends to expand the space, and the magnetic composition (material 42) accommodated in the space surrounded by the first lower punch 31 and the die 10 flows toward the shaft 2 side. 6A, the die 10 and the first lower punch 31 are lowered and the second upper punch 22 is lowered so that the second lower punch 32 is relatively raised with respect to the first lower punch 31. As a result, the magnetic composition filled in the cavity of the die 10 flows between the first upper punch 21 and the first lower punch 31. Since the filling depth of the magnetic composition between the first upper punch 21 and the first lower punch 31 is larger than between the second upper punch 22 and the second lower punch 32, the inner peripheral portion 3a and the inner portion as shown in FIG. When the bonded magnet 3 having the same length of the peripheral portion 3b is molded, the compressibility of the magnetic composition existing between the first upper punch 21 and the first lower punch 31 is such that the second upper punch 22 and the second lower punch 31 The compressibility of the magnetic composition existing between the punches 32 becomes larger. Thereby, the outer peripheral side portion 3a having a high density is formed by applying a forming pressure between the first upper punch 21 and the first lower punch 31, and the forming between the second upper punch 22 and the second lower punch 32 is performed. The inner peripheral side portion 3b having a small density is formed by applying pressure.

FIG. 7 is a graph showing the relationship between the molding pressure to be applied and the resulting molded body density. In FIG. 7, the horizontal axis represents the molding pressure (t / cm ² ), the vertical axis represents the molding density (g / cm ³ ), and the conditions (materials used) are changed in FIG. Two examples are shown. The molding pressure and the density of the compact have a linear relationship, and the outer circumference side portion 3a and the inner circumference side portion 3b of the bonded magnet 3 are respectively desired by adjusting the molding pressure in the molding process described above. Can be obtained.

  Contrary to the second embodiment described above, the shaft has a central portion in the axial direction that has a smaller diameter than both ends, and the entire region of the central portion of the shaft and a partial region on the central portion side of both ends are provided. The present invention can also be applied to a shaft-integrated bonded magnet having a structure in which a bonded magnet is integrally provided. Even in this configuration, as in the second embodiment, the coupling force between the shaft and the bond magnet is high, and the pull-out strength in the axial direction between the shaft and the bond magnet is excellent.

  In the above-described embodiment, there is a difference in density between the two portions of the bonded magnet 3 (the outer peripheral side portion 3a and the inner peripheral side portion 3b). However, the outer peripheral side has a higher density than the inner peripheral side. Moreover, you may make it make a difference in a density in three or more parts.

  In the embodiment described above, the bond magnet 3 is composed of a mixture (compound) of magnetic powder and thermosetting resin, but the bond magnet 3 contains magnetic powder and anaerobic resin. It may be configured. A procedure for producing the shaft-integrated bonded magnet 1 in this case will be briefly described below.

  A molded body obtained by compression-molding the magnetic powder integrally with the shaft 2 by the procedure shown in FIGS. Here, the material 42 to be filled in the space 41 is different from the magnetic powder and resin mixture (compound) only in using, for example, an R-TN magnetic powder, and other procedures. Is the same as the procedure described above, and the description thereof is omitted.

  A low-viscosity anaerobic resin is immersed in the molded article after compression molding using an impregnation method and left to stand. After leaving, excess anaerobic resin is removed by washing. Here, since it has anaerobic property, only the anaerobic resin inside and on the surface layer portion is cured, so that excess anaerobic resin that has been in contact with other air can be easily and quickly removed by washing. Next, the molded body impregnated with the anaerobic resin is subjected to a heat treatment at about 150 to 180 ° C. to completely cure the anaerobic resin, and the shaft integrated type having the bond magnet 3 containing the magnetic powder and the anaerobic resin. The bonded magnet 1 is produced. For the impregnation, a known method such as a reduced pressure method or a pressurized method may be applied.

  With such a configuration including magnetic powder and anaerobic resin, it is possible to provide the shaft-integrated bond magnet 1 with a high filling rate of magnetic powder and less variation in strength, and the magnetic characteristics can be improved.

  In the manufacturing procedure of the shaft-integrated bonded magnet 1 described above, a lubricant may be added to the mixture 42 of the magnetic powder and the thermosetting resin, or the material 42 including only the magnetic powder. By adding such a lubricant, the friction between the material 42 and the die 10 can be reduced, and the life of the molding apparatus can be extended.

  The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Shaft integrated bond magnet 2 Shaft 2a Center part 2b One end part 2c Other end part 3 Bond magnet 3a Outer peripheral part 3b Inner peripheral part

Claims (5)

In the shaft-integrated bond magnet in which the cylindrical bond magnet is integrally provided on the peripheral surface of the columnar shaft,
The shaft-integrated bond magnet is characterized in that the density on the outer peripheral side of the bond magnet is larger than the density on the inner peripheral side of the bond magnet.   The density of the region from the outer periphery of the bond magnet to at least 2 mm in the direction perpendicular to the length direction of the shaft is defined as the density on the outer periphery side of the bond magnet, and the length of the shaft from the thickest outer diameter of the shaft The density difference between the inner peripheral side and the outer peripheral side of the bond magnet is 2%, where the density of the region up to at least 2 mm toward the bond magnet in the direction perpendicular to the direction is the density on the inner peripheral side of the bond magnet. The shaft-integrated bonded magnet according to claim 1, wherein the bonded magnet is 5% or less.   The shaft-integrated bond magnet according to claim 2, wherein a density difference between the inner peripheral side and the outer peripheral side of the bond magnet is 2% or more and 3% or less.   The shaft-bonded bond magnet according to any one of claims 1 to 3, wherein the bond magnet includes magnetic powder and an anaerobic resin. The shaft has a central portion in the axial length direction having a larger diameter than both end portions, and the bond magnet is integrally formed so as to cover the entire region of the central portion of the shaft and a partial region on the central portion side of the both end portions. The shaft-integrated bonded magnet according to any one of claims 1 to 4, wherein the shaft-integrated bonded magnet is provided.

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