JP2019087569A - Shaft built-in bonded magnet and manufacturing method thereof - Google Patents

Abstract

To provide a shaft built-in bonded magnet capable of achieving weight saving and cost reduction, while maintaining sufficient magnetic properties, and capable of preventing breakdown of the bonded magnet even during high speed rotation, and to provide a manufacturing method of the shaft built-in bonded magnet capable of manufacturing the shaft built-in bonded magnet easily and accurately.SOLUTION: In a shaft built-in bonded magnet 1 where cylindrical bonded magnets 3 are provided integrally on the peripheral surface of a columnar shaft 2, the density on the outer peripheral side of the bonded magnet 3 (density of the outer peripheral side part 3a) is larger than the density on the inner peripheral side (density of the inner peripheral side part 3b). The outer peripheral surface of the bonded magnet 3 is covered with a protective cover 4. The central part 2a of the shaft 2 in the axial length direction has a larger diameter than those of both ends (one end 2b and the other end 2c), and the bonded magnet 3 is provided integrally to cover the whole area of the central part 2a of the shaft 2, and the partial area of both ends (one end 2b and the other end 2c) on the central part 2a side.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a shaft integrated bonded magnet used for various motors and a method of manufacturing the same.

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

  Patent Document 1 discloses such a shaft-integrated bonded magnet and a method of manufacturing the same. In Patent Document 1, a support member made of a rotor yoke having a rotor shaft inserted therein is disposed in a mold of a compression molding apparatus, and Nd-Fe-B magnetic powder and epoxy resin are provided around the support member. A shaft-integrated type bonded magnet is described, which is obtained by supplying a magnetic composition as described above and pressing it.

  According to Patent Document 1, it is possible to relatively easily provide a shaft integrated type 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 achieve miniaturization and high performance of the motor.

  By the way, in the shaft-integrated bond magnet, since the bond magnet integrated in the shaft has low mechanical strength, it may be broken and scattered when it is rotated at high speed. Therefore, in order to prevent such a situation, it is known to provide a cylindrical protective cover on the outer peripheral surface of the bond magnet to enhance the structural reliability. For example, Patent Document 2 discloses a configuration in which a protective cover made of fiber reinforced plastic is provided.

JP-A-6-140235 JP-A-8-107641

  In the conventional shaft-integrated type bonded magnet including Patent Document 1, the magnetic powder of a portion which does not effectively work on the external magnetic flux when incorporated in the motor is formed because the density is uniformly formed over the entire bonded magnet. There is a problem of being wasted.

  In patent document 2, after producing a shaft integral type bond magnet and a protection cover separately, a bond magnet is inserted in a protection cover, and both are pasted up with adhesives. Patent Document 2 also describes that the protective cover may be attached to the bonded magnet by press-fitting or cold-fitting.

  In the method of Patent Document 2, after the bond magnet is formed by the forming apparatus, the protective cover is attached to the bond magnet in a step different from the forming step, so the number of manufacturing steps is increased and the cost is increased. There is a problem of In the press-in method, in order to obtain a necessary and sufficient fastening force between the bond magnet and the protective cover, it is necessary to provide a fitting margin of about 0.05 to 0.1% of the outer diameter of the bond magnet. Since stress is applied to the bond magnet at the time of press fitting, there is a problem that the bond magnet is broken. On the other hand, in the cold fitting method, there is a problem that the bond magnet is broken due to the thermal shock due to the rapid temperature change in the press-in process, and the fitting can not be performed halfway due to the rapid temperature change during the operation.

  The present invention has been made in view of such circumstances, and by changing the density in the radial direction of the bonded magnet, it is possible to achieve weight reduction and cost reduction while maintaining sufficient magnetic characteristics, and By providing a protective cover on the outer periphery of the magnet, it is possible to simply and precisely manufacture a shaft-integrated bond magnet capable of preventing breakage of the bond magnet even at high-speed rotation, and this shaft-integrated bond magnet. An object of the present invention is to provide a method of manufacturing a shaft-integrated 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 the circumferential surface of a cylindrical shaft, wherein the density of the outer periphery of the bond magnet is the above It is characterized by providing the protective cover which coat | covered the outer peripheral surface of the said bond magnet larger than the density of the inner peripheral side of a bond 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 bond magnet, and the density on the outer peripheral side is larger than the density on the inner peripheral side. Increase the density and increase the amount of magnetic powder per unit volume on the outer circumference side that works effectively for the external magnetic flux when incorporated into the motor, and the density for the inner circumference side that does not work effectively for the external magnetic flux The size is reduced to reduce the amount of magnetic powder per unit volume. Therefore, sufficient magnetic characteristics can be obtained even if the overall weight is reduced. Further, in the present invention, since the protective cover is provided on the outer peripheral surface of the bond magnet, the protective cover receives the reaction against the centrifugal force generated at the time of rotation by the protective cover. Is prevented.

  The shaft-integrated bonded magnet according to the present invention is characterized in that the protective cover is made of carbon fiber reinforced plastic.

  In the present invention, a protective cover made of carbon fiber reinforced plastic is provided. Since carbon fiber reinforced plastic has higher strength than metal materials, it can function well even with a small thickness. Since carbon fiber reinforced plastic is lighter than metal materials, the increase in overall weight is small even with a protective cover.

  In the shaft-integrated type bonded magnet according to the present invention, the central portion of the shaft in the axial length direction has a diameter larger than that of both end portions, and the entire region of the central portion of the shaft and a part of the central portion side of both ends It is characterized in that the bond magnet is integrally provided to cover the area.

  In the present invention, a cylindrical shaft whose center in the axial length direction is larger in diameter than both ends is cylindrically covered so as to cover the entire area of the center of the shaft and a partial region on the center side of both ends. The bond 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.

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

  In the present invention, the bonded magnet contains the magnetic powder and the anaerobic resin. Therefore, since the excess anaerobic resin which touched the air can be easily removed by washing etc., the filling rate of magnetic powder can be made high in the state which had high strength.

  In the method of manufacturing a shaft-integrated bonded magnet according to the present invention, a cylindrical bonded magnet is integrally provided on the circumferential surface of a cylindrical shaft, and the density on the outer peripheral side of the bonded magnet is greater than the density on the inner peripheral side. A method of manufacturing a shaft-integrated type bonded magnet having a protective cover by covering the outer peripheral surface of the bond magnet using a forming apparatus, wherein a step of arranging a cylindrical protective cover on the forming apparatus A step of compression molding a mixture of a magnetic powder and a resin integrally with the shaft in the molding device to produce a molded body, and springback produced when the produced molded body is extracted from the molding device And utilizing the step of pressing the protective cover into the molded body.

  In the present invention, a molded body and a protective cover are produced using a pressure generated by springback generated when a molded body produced by compression molding a mixture of magnetic powder and resin integrally with a shaft is extracted from a molding apparatus. Crimp the Therefore, a protective cover can be attached in series using a molding device that performs compression molding, and a shaft-integrated bonded magnet with a protective cover can be easily manufactured with a small number of manufacturing steps.

  In the method of manufacturing a shaft-integrated bonded magnet according to the present invention, a cylindrical bonded magnet is integrally provided on the circumferential surface of a cylindrical shaft, and the density on the outer peripheral side of the bonded magnet is greater than the density on the inner peripheral side. A method of manufacturing a shaft-integrated type bonded magnet having a protective cover by covering the outer peripheral surface of the bond magnet using a forming apparatus, wherein a step of arranging a cylindrical protective cover on the forming apparatus And a step of compression molding the magnetic powder integrally with the shaft in the molding apparatus to produce a molded product, and springback generated when the produced molded product is extracted from the molding apparatus. The method may include the steps of: pressing the protective cover into the molded body; and impregnating the molded body with an anaerobic resin by a pressure impregnation method.

  In the present invention, the compact and the protective cover are pressure-bonded using the pressure generated by the spring back generated when the compact formed by compression molding the magnetic powder integrally with the shaft is extracted from the compacting apparatus. Therefore, a protective cover can be attached in series using a molding device that performs compression molding, and a shaft-integrated bonded magnet with a protective cover can be easily manufactured with a small number of manufacturing steps. In addition, since the excess anaerobic resin which has been in contact with the air can be easily removed by washing or the like after the anaerobic resin is impregnated into the molded body, the filling rate of the magnetic powder is increased in a state of having high strength. Manufactures a shaft-integrated bonded magnet with a protective cover.

  The method of manufacturing a shaft-integrated bonded magnet according to the present invention is characterized in that a lubricant is added to the mixture or the magnetic powder.

  In the present invention, a lubricant is added to the material of the bonded magnet. As a result, the friction between the material of the bond magnet and the die of the molding apparatus can be relieved, and the life of the molding apparatus can be extended.

  According to the shaft-integrated bond magnet of the present invention, even if the density of the entire shaft-integrated bond magnet is low, only the density of the part contributing to the motor characteristics can be selectively increased. While maintaining the above magnetic characteristics, weight reduction and cost reduction can be achieved, and breakage of the bond magnet can be prevented even at high speed rotation. Further, according to the method of manufacturing the shaft-integrated type bonded magnet of the present invention, the protective cover can be attached to the bonded magnet using spring back, so that the protective cover can be easily and accurately manufactured using one molding apparatus. It is possible to manufacture attached shaft integrated bond magnets.

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 molding pressure and a compact density.

  Hereinafter, the present invention will be described in detail based on the drawings showing the embodiments.

  FIG. 1 is a perspective view showing a shaft-integrated bonded magnet according to the present invention. The shaft-integrated bonded magnet 1 is configured such that a cylindrical shaft 2 and a cylindrical bonded magnet 3 are integrated, and the outer peripheral surface of the bonded magnet 3 is covered with a thin cylindrical protective cover 4. 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 showing the shaft-integrated bonded magnet 1 of the first embodiment. The shaft 2 in the shaft-integrated bonded magnet 1 of the first embodiment has a cylindrical shape whose entire area has an equal diameter. The bond magnet 3 is integrally provided in such a manner as to cover the outer peripheral surface of the central portion in the axial direction of the shaft 2. Moreover, the protective cover 4 is integrally provided in the aspect which covers the outer peripheral surface of the bond magnet 3. FIG.

  In the shaft-integrated bonded 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 bonded magnet 3 are 18 mm and 20 mm, respectively. The thickness of the protective cover 4 is 0.4 mm. Note that this dimension is merely an example, and the length and diameter of the shaft 2, the length and outer diameter of the bond magnet 3, and the thickness of the protective cover 4 may be appropriately set according to the required specifications. .

  FIG. 3 is a cross-sectional view showing the shaft-integrated bonded magnet 1 of the second embodiment. The shaft 2 in the shaft-integrated type bonded magnet 1 according to the second embodiment has a cylindrical shape as a whole, but the central portion 2a in the axial length direction has a diameter larger than that of the both ends. Bond magnet covering the outer peripheral surface of the entire area of the large-diameter central portion 2a of the shaft 2 and the outer peripheral surface of a partial region on the central portion 2a side of both ends (one end 2b and the other end 2c) 3 are integrally provided. Then, as in the first embodiment, the outer peripheral surface of the bond magnet 3 is covered with a thin cylindrical protective cover 4.

  In the shaft-integrated type 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 ends (one end 2b and the other end 2c) are 55 mm and 7 mm, respectively. The bond magnet 3 has a length of 18 mm and an outer diameter of 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. Also, for example, the thickness of the protective cover 4 is 0.4 mm. Note that 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, the lengths L1 to L6 of each part, and the thickness of the protective cover 4 are required specifications. It may be set appropriately according to

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

  As the magnetic powder of the bond magnet 3, rare earth magnetic powder, ferrite magnetic powder, etc. can be used. As a rare earth magnetic powder, R-T-B magnetic powder (R is at least one rare earth element and always contains either Nd or Pr, T is Fe or Fe and Co, B is boron) Part can be replaced by C (carbon), R-T-N based magnetic powder (R is at least one rare earth element and always contains Sm, T is an iron group element and N is nitrogen), etc. Can be mentioned. The shape of the R-T-B-based magnetic powder is preferably flat (for example, shape aspect ratio of powder particles = short diameter / long diameter is 0.3 or less). By using the R-T-B-based magnetic powder having a flat shape, the magnetic powder can be easily laminated at the time of compression molding of the material (mixture of magnetic powder and resin). In addition, it becomes difficult to form voids or resin accumulation between magnetic powders at the time of molding, and high-density packing becomes possible. The average particle diameter of the R-T-B based magnetic powder is preferably 20 to 300 μm, and more preferably 40 to 250 μm. Here, the average particle diameter is an arithmetic average diameter of the volume distribution, and is measured using a laser diffraction type particle size distribution measuring apparatus.

  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, epoxy resin, phenol resin, polyimide resin and the like.

  The protective cover 4 is made of carbon fiber reinforced plastic (CFRP), and is produced, for example, as follows. A carbon fiber having an outer diameter of several μm is impregnated with a liquid epoxy resin, and the carbon fiber impregnated with the epoxy resin is wound around a rotating cylindrical core and reciprocated to form a spirally wound carbon fiber After making the cross winding which each crossed, this winding body is heated and an epoxy resin is hardened. The thickness of the protective cover 4 is preferably about 0.3 to 0.5 mm.

  By making the protective cover 4 of carbon fiber reinforced plastic, the following advantages can be obtained. Since carbon fiber reinforced plastic has high tensile strength compared to metal materials such as iron and SUS, it can perform a sufficient function even with a thin thickness. Further, since the carbon fiber reinforced plastic is lighter than metal materials such as iron and SUS, even if the protective cover 4 is provided, the increase in the overall weight of the shaft-integrated bonded magnet 1 can be reduced.

  The material of the protective cover 4 is not limited to carbon fiber reinforced plastic, and organic high strength fiber may be used. In particular, when non-conductive fibers are used, unlike when conductive materials are used, no eddy current is generated due to the rotating magnetic field, so that there is an advantage that losses due to eddy currents do not occur.

  In the shaft-integrated type bonded magnet 1 according to the present invention having such a configuration, the cylinder integrally provided on the circumferential 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 bonded magnet 3 is formed by compression molding of a mixture of magnetic powder and resin (magnetic composition: compound) to be a material, and the difference in density is defined by the ratio of the void. That is, the ratio of voids in the outer peripheral portion 3a is smaller than the ratio of voids 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 portion 3a and the inner peripheral portion 3b of the bond magnet 3 is 2% to 5%, and more preferably 2% to 3%. If the density difference is less than 2%, the weight reduction that is the effect of the present invention can not 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 of the density difference (strain, crack, etc.) in the boundary portion. Therefore, in order to achieve weight reduction while maintaining sufficient magnetic characteristics when incorporated into a motor, the density difference is set to 2% or more and 5% or less. Here, the density of the outer peripheral portion 3 a of the bond magnet 3 refers to the density of the region from the outer periphery of the bond magnet 3 to at least 2 mm in the direction perpendicular to the longitudinal direction of the shaft 2. The density of the side portion 3b refers to the density of the region from the thickest outer diameter of the shaft 2 toward the bond magnet 3 to at least 2 mm. The measurement of the density is carried out using Archimedes method after cutting out after producing the bonded magnet.

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

  In the shaft-integrated type bonded magnet 1 of the present invention, there is a difference in density between the inner peripheral side (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 Is greater than the density of Increase the density and increase the amount of magnetic powder per unit volume on the outer circumference side that works effectively for the external magnetic flux when incorporated into the motor, and the density for the inner circumference side that does not work effectively for the external magnetic flux The size is reduced to reduce the amount of magnetic powder per unit volume. Therefore, sufficient magnetic characteristics can be obtained even if the weight of the whole is reduced.

  In the shaft-integrated type bonded magnet 1 according to the present invention, the outer peripheral surface of the bonded magnet 3 is covered with the protective cover 4 made of carbon fiber reinforced plastic in any of the first embodiment and the second embodiment. It is done. Therefore, since the protective cover 4 can receive the reaction force against the centrifugal force generated at the time of rotation of the shaft-integrated bond magnet 1, the bond magnet 3 is not broken even at high-speed rotation.

  Unlike the first embodiment in which the diameter of the shaft 2 is the same throughout the axial length direction, in the second embodiment, the diameter of the central portion 2 a in the axial direction of the shaft 2 is changed to both end portions (one end 2 b and the other 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 axial disengagement between the shaft 2 and the bond magnet 3 is obtained. It is excellent in strength.

  Hereinafter, specific dimensions and densities of the outer peripheral side portion 3a and the inner peripheral side portion 3b having such differences in density will be described as an example of the first embodiment. 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 the invention examples (Nos. 2, 4 and 6) in the case where the outer diameter D1 of the outer peripheral side portion 3a is 20 mm. The diameter of the shaft 2 was 2 mm. As the number of magnetic poles increases, the magnetic path is not formed to the inside, so sufficient magnetic characteristics can be obtained even if the inner peripheral portion 3b whose density is reduced is increased. Table 1 also shows examples (No. 1, 3, 5) of a shaft-integrated bonded magnet as a comparative example in which the density of the bonded magnet is uniform over the entire region. Examples of the present invention and comparative examples are materials (consisting of magnetic powder and resin. Magnetic powder is R-T-B based magnetic powder, resin is epoxy resin. R-T-B based magnetic powder is MQP-14 A magnetic powder of -9 (manufactured by Molycorp) was used.The composition of MQP-14-9 was 16.7% by mass Nd, 3.8% by mass La, 5.5% by mass Pr, 1.0% by mass. The average particle diameter of MQP-14-9 is 100 μm, and the resin is 2% by mass of the whole material), and the shape and size are the same. The amount of magnetic flux measured by the flux meter was measured by connecting a Helmholtz coil to a LakeShore flux meter manufactured by Toyo Technica. For example, No. 1 of the example of the present invention. In No. 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 3 b 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 No. 2. In No. 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 total weight is 33.2 g. No. 1 and No. 1 When 2 is compared, a weight reduction of 0.1 g can be achieved.

  Table 2 shows the invention examples (Nos. 8, 10, 12) in the case where the outer diameter D1 of the outer peripheral side portion 3a is 30 mm, and the comparative examples (Nos. 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 inventive 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 (invention example) according to the second embodiment and the comparative example (when there is no density difference in the entire bonded magnet) will be described. The magnetic powder and the resin used for the bonded magnet in the comparative example and the inventive example are respectively Nd-Fe-B based magnetic powder (magnetic powder of MQP-14-9 (made by Molycorp)) and 2% by mass with an average particle diameter of 100 μm. It is an epoxy resin. The number of magnetic 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 portion 3 a (outer diameter 20 mm) and the inner peripheral portion 3 b (outer diameter) of the bonded magnet 7 mm) The respective densities were 6.1 g / cm ³ and 5.9 g / cm ³ . As a result, while the weight was 31 g in the comparative example, it was 30 g in the inventive example, and it was confirmed that a weight reduction of about 3% was achieved. Therefore, it is understood that in the example of the present invention, 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 is not detached or broken even by the rotation of 65000 rpm, and the mechanical characteristics are also excellent.

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

  No. 1 in which the density difference is in the range of 2 to 5%. 14-No. It can be seen that weight reduction can be achieved while maintaining sufficient magnetic properties at 16.

On the other hand, No. 1 in which the density difference is 10%. In the case of No. 18, although the weight saving is remarkable, the density of the inner peripheral side portion 3b is too low at 5.5 g / cm ³ , so there is a possibility that a problem may occur in the strength of the bond magnet 3. Also, No. 1 with a density difference of 7%. In No. 17, the density of the inner peripheral side portion 3b is 5.7 g / cm ³ which is the minimum necessary in consideration of the strength, but it is not preferable in consideration of the decrease in density due to the variation in mass production. On the other hand, no. Naturally, weight reduction can not be achieved at 13.

  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 realizing high levels of magnetic properties and strength.

  In each example shown in Table 3, the magnetic flux amount by the flux meter does not have a large difference 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 Since the thickness of the high portion is large and the number of magnetic poles is as large as eight, it is considered that only the vicinity of the surface of the bond magnet 3 is magnetized.

  Hereinafter, the procedure of manufacturing the shaft-integrated bonded magnet 1 according to the second embodiment of the present invention will be described with reference to FIGS. 4 to 6 which show the procedure of the manufacturing process. The shaft-integrated bonded magnet according to the first embodiment differs 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 described later is the shaft according to the second embodiment. It is the same as an integral bond magnet.

  FIG. 4A shows the start position (hereinafter referred to as “fixed position”) of the molding operation of the molding device 5 used in the manufacturing process. The molding apparatus 5 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 long cylindrical second upper punch having an outer diameter substantially equal to the inner diameter of the first upper punch 21. It has a triple configuration including an upper punch 22 and an elongated cylindrical upper core 23 having a diameter substantially equal to the inner diameter of the second upper punch 22 and can be inserted from above in the die 10. The first upper punch 21 can be inserted vertically through the die 10, the second upper punch 22 can be inserted vertically through the first upper punch 21, and the upper core 23 is inserted into the second upper punch 22. Can be inserted vertically. The movement (rising / falling) of the first upper punch 21, the movement (rising / falling) of the second upper punch 22, and the movement (rising / falling) of the upper core 23 can be performed independently of each other.

  The lower die 30 has a first cylindrical lower punch 31 having an outer diameter substantially equal to the inner diameter of the die 10, and an elongated cylindrical first lower punch 31 having an outer diameter substantially equal to the inner diameter of the first lower punch 31. It has a triple configuration including a second lower punch 32 and an elongated cylindrical lower core 33 having a diameter substantially equal to the inner diameter of the second lower punch 32, and can be inserted from below in the die 10. The first lower punch 31 can be inserted vertically through the die 10, the second lower punch 32 can be inserted vertically through the first lower punch 31, and the lower core 33 is inserted into the second lower punch 32. Can be inserted vertically. The movement (rising / falling) of the first lower punch 31, the movement (rising / falling) of the second lower punch 32, and the movement (rising / falling) 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 material 42 (a mixture of magnetic powder and resin (magnetic composition)) of the bonded magnet 3 is filled in the space 41. The descent distance d1 (the depth of the space 41) at this time is the length (the length L1 shown in FIG. 3) of the bond magnet 3 in the shaft integrated bond magnet 1 to be manufactured and the material in the compression molding step described later. It is determined in consideration of the compression ratio of 42.

  Next, as shown in FIG. 4D, the thin cylindrical protective cover 4 prepared in advance is coaxially disposed on the upper surface of the die 10 with respect to the die 10, and the desired jig (not shown) is used. Fix the position. The inner diameter of the protective cover 4 is slightly larger than the inner diameter of the die 10. The difference in the inner diameter is determined in accordance with the amount of springback (the amount of increase in the outer diameter of the molded body 44) when the molded body 44 after compression molding described later is extracted from the die 10. That is, since the amount of springback in the case of using a magnetic composition as the material 42 is 0.6 to 1%, the inner diameter of the protective cover 4 is preferably 100.6% or less of the inner diameter of the die 10.

  Next, as shown in FIG. 4E, the lower core 33 is lowered to form an open portion 43 inside the second lower punch 32. The descent 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 in which the outer peripheral surface is not covered with the bond magnet 3 in the shaft integrated bond magnet 1 Ru. 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 2b of the shaft 2 prepared in advance is inserted into the opening 43. At this time, the shaft 2 is lowered until one end surface of the one end portion 2 b of the shaft 2 abuts on 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) or the like.

  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 abuts on one end surface of the other end 2 c of the shaft 2, and the shaft 2 is held by 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 covering a partial area of the other end 2 c of the shaft 2. The descent positions of the first upper punch 21 and the second upper punch 22 are determined in consideration of the length of the area 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 bond magnet 1 Be done. That is, it is determined in consideration of the lengths L2 and L3 shown in FIG. 3 and the compression rate.

  When forming the open portion 43 inside the second lower punch 32 by lowering the lower core 33 in FIG. 4E instead of the embodiment based on FIG. 4E to FIG. 5A, the descent distance d2 (open In the shaft-integrated type bonded magnet 1, the length (the length L6 shown in FIG. 3) of the region of the end portion 2b of the shaft 2 whose outer peripheral surface is not covered with the bond magnet 3 The length corresponding to the sum of the length covered by the magnet 3 (the length L5 shown in FIG. 3) may be used. At this time, in FIG. 5A, the entire one end 2b of the shaft 2 is inserted into the open portion 43, and as a result, the boundary between the one end 2b and the central 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. 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 2b of the shaft 2, a part of the central part 2a and a part of the other end 2c are buried in the material 42. The descent distance of upper core 23 and lower core 33 and first upper punch 21 and second upper punch 22 at this time (position of upper core 23 and lower core 33 and first upper punch 21 and second upper punch 22 in FIG. 5B) In FIG. 5D, the outer peripheral surfaces of one end 2b and the other end 2c of the shaft 2 are bonded magnets 3 in the upper core 23 and lower core 33 and the distances to the first upper punch 21 and second upper punch 22). 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 rate.

  As shown in FIG. 5D, the first upper punch 21 and the second upper punch 22 are lowered until they abut the upper surface of the material 42 or 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.

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

  Further, in the embodiment based on FIG. 5B to FIG. 5D, the upper core 23 and the lower core 33 hold the shaft 2 in advance and interlock the upper core 23 and the lower core 33 while lowering the second lower punch 32. Instead of the process of immersing a part of the one end 2b of the shaft 2 and a part of the central part 2a and the other end 2c in the material 42, the shaft 2 is made by the upper core 23 and the lower core 33 in advance. Alternatively, only 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 in a state where the shaft 2 is placed on the lower core 33 without holding the second lower punch 32. Further, the lowering of the shaft 2 may be performed manually or using a dedicated jig (dedicated device) or the like.

  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. The lowering of the die 10 and the first lower punch 31 causes the second lower punch 32 to rise relatively.

  Thereafter, as shown in FIG. 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 holding the shaft 2 by the upper core 23 and the lower core 33. Let Here, the descent 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 become the same. Further, the raising amounts of the first lower punch 31 and the second lower punch 32 are adjusted so that the height positions of the surfaces in contact with the material 42 of the first lower punch 31 and the second lower punch 32 become the same. The lowering of the die 10 causes the first lower punch 31 and the second lower punch 32 to rise relatively. Then, the material 42 is compressed by the first upper punch 21 and the second upper punch 22 and the first lower punch 31 and the second lower punch 32 from two directions, the lower direction and the upper direction, to obtain the shaft 2 and the material 42. Integrated and molded.

  Although the die 10 is lowered, the first lower punch 31 and the second lower punch 32 may be directly raised. In the embodiment based on FIGS. 6A and 6B, the descent distance of the die 10 and the descent distance 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 for raising the first lower punch 31 and the second lower punch 32 will be described later. It may be determined in consideration of the shape of the molded product 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. Here, the raising operation is performed until the die 10, the first lower punch 31, and the second lower punch 32 return to the home position.

  Here, when the compact 44 after compression molding is extracted from the die 10, it expands in the outer diameter direction by spring back, and the compact is formed on the inner peripheral surface of the protective cover 4 disposed on the upper surface of the die 10. The outer peripheral surface of 44 is crimped. Thereby, the molded body 44 (bond magnet 3) and the protective cover 4 are joined in a strongly pressure-bonded state. The amount of springback in the material 42 of this example is 0.6 to 1% as described above. Therefore, when the degree of increase in the outer diameter of the molded body 44 due to the spring back is 0.6% of the lower limit, when the inner diameter of the protective cover 4 is larger than 100.6% of the inner diameter of the die 10 4 can not be crimped. In this example, since the inner diameter of the protective cover 4 is 100.6% or less of the inner diameter of the die 10, the molded body 44 (bond magnet 3) can be securely crimped to the protective cover 4 by spring back.

  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 the home position. Thereafter, the molded article in which the protective cover 4 is pressure-bonded to the molded body 44 is taken out from the die 10. 6A to 6D, only the die 10 is lowered and the molded product is taken out from the die 10. Then, the die 10, the first upper punch 21, the second upper punch 22, and the upper die 22 are removed. The core 23, the first lower punch 31, the second lower punch 32, and the lower core 33 may all be operated to return to the home position.

  The molded product taken out is subjected to a heat treatment at 200 ° C. for 1 hour to cure the resin. Thereby, a shaft-integrated bonded magnet 1 with a protective cover 4 having a desired density and shape is obtained.

  In the embodiment described above, the disposing step of disposing the protective cover 4 on the upper surface of the die 10 is performed immediately after the step of filling the material 42 (FIG. 4C). It is not limited. For example, the protective cover 4 may be disposed before the step of filling the material 42, or the protective cover 4 may be disposed after the filled material 42 is compressed. The protective cover 4 may be disposed on the die 10 when the molded body 44 is removed from the die 10.

  In the above-described forming process, as shown in FIG. 5C, the second lower punch 32 which has the same height as the upper surface of the die 10 by lowering the second lower punch 32, the upper core 23, and the lower core 33 in conjunction with each other. Is lowered to expand the space, and the magnetic composition (material 42) contained in the space surrounded by the first lower punch 31 and the die 10 flows to the shaft 2 side. Further, as shown in FIG. 6A, the second lower punch 32 is raised relative to the first lower punch 31 by lowering the die 10 and the first lower punch 31 and lowering the second upper punch 22. 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 that between the second upper punch 22 and the second lower punch 32, the inside of the outer peripheral portion 3a as shown in FIG. When molding the bonded magnet 3 having the same length in the circumferential side portion 3b, the compression ratio of the magnetic composition existing between the first upper punch 21 and the first lower punch 31 is the second upper punch 22 and the second lower. It becomes larger than the compression ratio of the magnetic composition existing between the punches 32. As a result, the outer peripheral portion 3a having a large density is formed by application of the forming pressure between the first upper punch 21 and the first lower punch 31, and the formation between the second upper punch 22 and the second lower punch 32 is performed. By application of pressure, the inner peripheral portion 3b having a small density is formed.

FIG. 7 is a graph showing the relationship between the molding pressure to be applied and the obtained green density. In FIG. 7, the abscissa represents the molding pressure (t / cm ² ), the ordinate represents the density of the compact (g / cm ³ ), and FIG. 7 changed the conditions (materials used) Two examples are shown. The molding pressure and the density of the molded body exhibit a linear relationship, and by adjusting the molding pressure in the above-described molding process, desired on the outer peripheral portion 3a and the inner peripheral portion 3b of the bonded magnet 3 are desired. Density can be obtained.

  Hereinafter, other embodiments for manufacturing the shaft integrated bond magnet 1 with the protective cover 4 will be described. In the embodiment described above, a mixture of magnetic powder and resin (magnetic composition: compound) is used as the material 42 filled in the space 41, but in the following embodiment, for example, R-T- Only N-based magnetic powder is used as the material 42.

  According to the procedure shown in FIGS. 4 to 6 as described above, the magnetic powder is integrally compression-molded on the shaft 2 to produce a molded body 44. Here, only the material 42 to be filled in the space 41 is different, and the other procedures are the same as the procedures described above, so the description thereof will be omitted.

  Also in this embodiment, the protective cover 4 is crimped to the molded body 44 (bonded magnet 3) using spring back when the molded body 44 is extracted from the die 10. However, when only magnetic powder is used as the material 42, the amount of spring back is 0.06 to 0.1%. Therefore, the inner diameter of the protective cover 4 is preferably set to 100.06% or less of the inner diameter of the die 10. In this way, even if the degree of increase in the outer diameter of the molded body 44 due to the spring back is 0.06% of the lower limit, the spring back when the molded body 44 is extracted from the die 10 The protective cover 4 can be securely crimped to the bond magnet 3).

  A low viscosity anaerobic resin is impregnated and left in a molded article in which the protective cover 4 is pressure-bonded to the molded body 44 using a pressure impregnation method. After standing, the excess anaerobic resin is removed by washing. Here, since the anaerobic resin is used, only the anaerobic resin in the inner and surface layers of the magnet is cured, so that the excess anaerobic resin that has been in contact with the air other than that can be easily and rapidly removed by washing. Next, the molded article 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 protective cover 4 having the bonded magnet 3 containing the magnetic powder and the anaerobic resin Manufacture a shaft-integrated bonded magnet 1 of

  In a configuration including such magnetic powder and anaerobic resin, it is possible to provide a shaft-integrated type bonded magnet 1 with a protective cover 4 that has a high filling ratio of magnetic powder and little variation in strength, and aims to improve the magnetic characteristics. it can.

  In the manufacturing method of the present invention, as described above, the pressure generated by spring back generated when the produced molded body 44 (bond magnet 3) is extracted from the molding apparatus 5 (die 10) is used to form the molded body 44 (bond Since the magnet 3) and the protective cover 4 are crimped, the protective cover 4 can be attached in series using the molding apparatus 5 that performs the compression molding process, so the protective cover 4 can be attached easily with a small number of manufacturing steps. The shaft integrated bond magnet 1 can be manufactured with high accuracy.

  In the method of manufacturing the shaft-integrated bonded magnet 1 described above, a lubricant may be added to the mixture of the magnetic powder and the thermosetting resin, or the material 42 which is only the magnetic powder. By adding such a lubricant, the friction between the material 42 and the die 10 is relieved, the damage on the die 10 is reduced, and the life of the molding apparatus 5 can be prolonged.

  In contrast to the second embodiment described above, the shaft has a central portion in the axial length direction that is smaller in 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 The present invention can also be applied to a shaft-integrated bonded magnet having a configuration in which a bonded magnet is integrally provided. Also in this configuration, as in the second embodiment, the coupling force between the shaft and the bond magnet is high, and the axial removal strength between the shaft and the bond magnet is excellent.

  In the embodiment described above, although there is a difference in density with respect to two portions (the outer peripheral side portion 3a and the inner peripheral side portion 3b) of the bond magnet 3, the outer peripheral side has a larger density than the inner peripheral side Alternatively, the density may be different in three or more parts.

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

Reference Signs List 1 shaft-integrated bonded magnet 2 shaft 2a central portion 2b one end 2c other end 3 bonded magnet 3a outer peripheral portion 3b inner peripheral portion 4 protective cover 5 forming apparatus 10 die 42 material 44 molded body

Claims (7)

In a shaft-integrated bond magnet in which a cylindrical bond magnet is integrally provided on the circumferential surface of a cylindrical shaft,
A shaft integral type bonded magnet comprising a protective cover which has a density on the outer peripheral side of the bond magnet larger than a density on the inner peripheral side of the bond magnet and covers the outer peripheral surface of the bond magnet.   The shaft integral bonded magnet according to claim 1, wherein the protective cover is made of carbon fiber reinforced plastic.   The central portion of the shaft in the axial direction has a diameter larger than that of both ends, and the bond magnet integrally covers the entire area of the central portion of the shaft and a partial region on the central portion side of the both ends. The shaft-integrated bonded magnet according to claim 1 or 2, wherein the magnet is provided.   The shaft-integrated bonded magnet according to any one of claims 1 to 3, wherein the bonded magnet includes a magnetic powder and an anaerobic resin. A cylindrical bond magnet is integrally provided on the circumferential surface of a cylindrical shaft, the density on the outer circumferential side of the bond magnet is greater than the density on the inner circumferential side, and the protective cover covers the outer circumferential surface of the bond magnet. A method of manufacturing a shaft-integrated bonded magnet provided using a molding apparatus, comprising:
Placing a cylindrical protective cover on the forming device;
Producing a molded body by compression molding a mixture of magnetic powder and resin integrally with a shaft in the molding apparatus;
And a step of press-fitting the protective cover into the molded body by utilizing a spring back generated when the produced molded body is removed from the molding apparatus. A cylindrical bond magnet is integrally provided on the circumferential surface of a cylindrical shaft, the density on the outer circumferential side of the bond magnet is greater than the density on the inner circumferential side, and the protective cover covers the outer circumferential surface of the bond magnet. A method of manufacturing a shaft-integrated bonded magnet provided using a molding apparatus, comprising:
Placing a cylindrical protective cover on the forming device;
Forming a compact by compression molding the magnetic powder integrally with the shaft in the molding apparatus;
Press-fitting the protective cover into the molded body by utilizing a spring back generated when the manufactured molded body is removed from the molding apparatus;
And D. a step of impregnating the molded article with an anaerobic resin by a pressure impregnation method.   7. A method of manufacturing a shaft-integrated bonded magnet according to claim 5, wherein a lubricant is added to the mixture or the magnetic powder.

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