Brushless SPM motor and manufacturing method of its rotor

Abstract

To provide a motor using a rare-earth anisotropic bonded magnet for achieving high-speed rotation and high output.SOLUTION: A rotor (2) of a brushless SPW motor includes: an arc-shaped magnet having the maximum energy product of at least 10 MGOe, the arc-shaped magnet being made of a magnetic material with magnetic properties magnetically isotropic in a radial direction. The arc-shaped magnet is magnetized with at least four magnetic poles so that N poles and S poles are alternately magnetized in a pseudo-anisotropic manner by injection molding of a rare-earth anisotropic bonded magnet. The arc-shaped magnet is firmly fixed to the outer peripheral part of a rotor body by a metal adhesive to enhance resistance to centrifugal force.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a surface permanent magnet synchronous machine (hereinafter referred to as an SPM motor) in which a ring-shaped rare earth anisotropic bonded magnet is fixed to the outer periphery of the rotor, the rotor, and a method for manufacturing the rotor. [Background technology]

[0002] There are various types of electric motors (generators are also referred to simply as "motors"). Recently, with the development of inverter control and the widespread use of rare earth magnets with high magnetic properties, brushless motors have been attracting attention because they are energy-efficient, highly efficient, and offer high torque or output.

[0003] Brushless motors are broadly divided into surface permanent magnet motors (SPM), in which permanent magnets are arranged on the surface of the rotor, and interior permanent magnet motors (IPM), in which permanent magnets are embedded inside the rotor. SPM motors have excellent controllability and are mainly used in small motors. IPM motors are easy to obtain large output and are mainly used in power motors for power applications.

[0004] For small robot motors that require excellent controllability, products from the Swiss company Maxon are widely used, but there is a demand for motors that are at least 50% smaller, lighter, more powerful, and less expensive. To achieve this, efforts have been made to reduce size, weight, and increase power through higher speeds, and motors with rotation speeds of 60,000 to 100,000 RPM have recently been successfully developed. However, attempts to achieve even higher speeds have faced a major technological hurdle: the use of sintered neodymium magnets.

[0005] To solve this problem, Patent Document 1 discloses a polar-anisotropic rare earth bonded magnet and a permanent magnet motor. According to this invention, Sm-Fe-N based magnet powder, which has a better aligning magnetic field than Nd-Fe-B based magnet powder, is used as the rare earth magnet powder, and the maximum energy product is 3 to 14 MGOe. The manufacturing method involves producing a ring-shaped magnet by injection molding at a mold temperature of 80°C. The magnet has eight magnetic poles arranged alternately with north and south poles, and each pole is magnetized with polar anisotropy without using any magnetic material, as shown in Figure 6. However, the invention disclosed in Patent Document 1 has the drawback that the magnetic force is weak and the ring magnet is damaged by the centrifugal force at rotation speeds of 120,000 RPM or more.

[0006] In Patent Document 2, the pseudopolar anisotropic orientation is used to suppress the stress concentration that occurs between the magnet and the rotor surface during rotation, and the ring breakage problem is solved by increasing the adhesive strength between the magnet and the rotor surface. Furthermore, Patent Document 3 discloses that in addition to the measures described in Patent Document 2, the ring breakage problem can also be solved by dividing the magnet body.

[0007] However, in Patent Documents 2 and 3, the rotor is made by laminating thin stainless steel magnetic disks, and the laminated stainless steel magnet body has uniaxial anisotropy in cross section, not isotropy in the radial direction. If the magnetic poles are magnetized with pseudopolar anisotropy, asymmetry will appear in the magnetization state of the four magnetic poles, resulting in cogging torque problems. Furthermore, stress will be unevenly distributed in specific locations on the surface of the magnet body and rotor body, making them prone to damage when the rotational speed is increased to 160,000 RPM or more.

[0008] The present invention solves the heat generation problem of Maxon's sintered neodymium magnets, the centrifugal force problem of the invention in Patent Document 1, and the cogging torque problem of Patent Documents 2 and 3, and achieves a reduction in size and weight by 50% or more compared to current products. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-195714 [Patent Document 2] Patent No. 7426569 [Patent Document 3] Patent No. 7394428 Summary of the Invention [Problem to be solved by the invention]

[0010] The standard product for small robot motors that are widely used is that made by Maxon. To obtain great power, a two-pole magnetized neodymium sintered magnet is attached to the rotor, and this is used at 60,000 to 100,000 RPM, resulting in a small, high-output motor (Figures 8 and 9). Efforts to increase speed and performance beyond this are difficult due to the problem of heat generation in the neodymium sintered magnet.

[0011] Rare earth bonded magnets do not generate heat even when rotated at high speeds of over 120,000 RPM, but because their magnetic force is weak, it is difficult to simply replace them with sintered Nd magnets and make them smaller. Furthermore, when attaching sintered Nd magnets to the rotor, if mechanical asymmetry occurs due to uneven shape or poor weight balance, or if the magnetic field distribution created by the magnets becomes uneven in coaxiality, cogging torque and vibrations are more likely to occur while the motor is rotating.

[0012] Furthermore, high-speed rotation causes large centrifugal forces to act on the magnets attached to the surface, and if there is non-uniformity in the coaxiality, stress will concentrate in specific areas, causing peeling to begin from those areas, which will then lead to fatigue failure of the ring magnet. Simply replacing the ring magnet with a rare-earth bonded magnet that does not generate heat will not be enough to design a high-speed rotation motor.

[0013] The inventors have a track record of successfully reducing the size and weight of a small brush motor by 75% by increasing the magnetic poles from two to four and doubling the rotation speed from the conventional 3000 RPM to 6000 RPM (Fig. 10). In addition, a two-pole radially oriented ferrite magnet is converted into a compression-molded rare earth ring magnet, which is then Pseudopolar anisotropic magnetization By making the magnetic field distribution sinusoidal, smooth rotation is achieved. This design required half the magnet energy and reduced the motor weight to one-quarter, meaning eight times the performance per unit of magnet energy was achieved.

[0014] This experience suggests that even if the amount of magnetic energy used is reduced by replacing sintered Nd magnets with rare earth bonded magnets, i.e., by replacing magnets with inferior performance, it is entirely possible to make the motor 50% smaller and lighter if an eight-fold improvement in performance can be achieved through the structural design of the motor.

[0015] This invention was made in light of these circumstances, and was developed based on the idea that by using injection-molded rare earth magnets and magnetizing them with pseudopolar anisotropy, it is possible to improve the coaxiality of the rotor of an SPM motor, and by increasing the number of magnetic poles from two to four to reduce the magnetic force of the magnet and raising the motor rotation speed to 120,000 RPM or more, it is possible to achieve a 50% reduction in size and weight, and that pseudopolar anisotropy magnetization via magnetic material could solve the centrifugal force problem. Here, pseudopolar anisotropy means that the magnetic poles of the ring magnet and the magnetic material are integrated and anisotropically saturated, and the ring magnet and the magnetic material of the rotor are strongly bonded, which has the effect of generating a force that counteracts centrifugal force, and at the same time, the magnetic field emitted from the ring magnet of the rotor has a sinusoidal waveform. (Figure 6) . [Means for solving the problem]

[0016] The inventors first considered it important to enable high-speed rotation of over 160,000 RPM, and therefore investigated how to create a rotor with excellent coaxiality. To achieve this, they focused on injection-molded rare earth anisotropic bonded magnets. A precisely manufactured cylindrical rotor component is attached to a precision injection mold, and a bonded magnet is molded into the gap using injection molding technology. They realized that this would enable the creation of a rotor with extremely high coaxiality in terms of shape and weight balance.

[0017] Moreover, magnetically, a magnetic material having isotropic magnetic properties in the radial direction is used for the magnetic material of the rotor body, and the magnetic poles of the ring magnet are pseudo-polar anisotropically magnetized via this material. Symmetrically We found that the centrifugal force problem can be solved by doing this. This makes the strength of the pseudopolar anisotropically magnetized magnetic poles symmetrical, and the magnetic flux density distribution on the surface becomes a sinusoidal function. This makes it possible to suppress the cogging torque of the motor and the generation of vibration. To achieve this, we created a pseudopolar anisotropic mold to be used during injection molding and performed injection molding in a magnetic field. Magnetic materials with isotropic magnetic properties include heat-treated, drawn, and cold-pressed magnetic materials. Heat-treated products are isotropic in all directions, and naturally are isotropic in the radial direction as well. Drawn and cold-pressed products have axial anisotropy but are isotropic in the radial direction.

[0018] Next, the number of magnetic poles was increased from two to four to compensate for the decrease in magnetic force. Furthermore, the gap between the outer surface of the rotor magnet and the inner surface of the stator electromagnet was reduced from approximately 1.5 mm in the conventional Maxon product to less than 0.3 mm. This was only possible thanks to the rotor's excellent coaxiality. Furthermore, increasing the number of poles to six would enable further miniaturization.

[0019] As described above, by combining the following factors - the use of injection-molded rare earth anisotropic bonded magnets, making the magnetic poles polar anisotropic, increasing the number of magnetic poles from two to four or more, reducing the gap between the rotor and stator to 0.3 mm or less, and increasing the rotor rotation speed to 160,000 RPM or more - it has been discovered that it is possible to reduce the size of Maxon's widely used small motors by more than 50%.

[0020] The biggest problem in design and prototyping was whether the ring magnet could withstand the large centrifugal forces, and whether the adhesive strength between the ring magnet and the rotor body parts could withstand them. Even slight misalignment in coaxiality or vibration during motor rotation would cause stress to concentrate at specific points on the joint surface between the magnet and rotor, causing cracks to form there and eventually damaging the ring magnet. A common solution is to attach a non-magnetic shatterproof cover to the surface of the ring magnet and apply pressure from the outside to prevent damage from centrifugal forces. However, this increases the gap between the magnet and the stator, making it impossible to achieve sufficient miniaturization.

[0021] In addition to the bonding force of the adhesive that acts between the magnet and the magnetic material of the rotor body, the present invention strengthens the magnetic bonding force that acts between the magnet and the magnetic material of the rotor body by using pseudopolar anisotropic magnetization, thereby preventing the ring magnet from flying off due to centrifugal force.

[0022] Therefore, we decided to first provide grooves extending axially symmetrically around the outer periphery of the rotor body, the number of which is equal to the number of magnetic poles, and then attach injection-molded magnets. Injection Molded Magnets The convex parts of the rotor engage with the concave parts on the rotor surface, preventing the magnet from rotating. The stress acting on the interface between the two is the resultant of centrifugal force and rotational force, and the rotational force is absorbed by this stopper, reducing the stress acting on the interface.

[0023] Next, the outer periphery of the rotor body was given a wave-like or knurled texture to increase the adhesive surface area, and then a fine jagged texture of 0.5 to 10 μm was added, and a resin layer was formed on top of this using a metal adhesive to firmly fix the ring magnet to the outer periphery of the rotor body.

[0024] Furthermore, the magnetic poles utilize the large magnetic force acting between the magnet body and the magnetic material by integrally magnetizing them with pseudopolar anisotropy, strengthening the bonding force between them. These measures were found to avoid the centrifugal force problem. In other words, high-speed rotation was made possible without installing a non-magnetic shatterproof case on the surface of the ring magnet.

[0025] By improving the bonding strength between the magnet and rotor, the motor's rotation speed has been increased from over 120,000 RPM to over 160,000 RPM compared to the motors disclosed in Patent Documents 2 and 3, and the motor size has been reduced from an outer diameter of 20 mm or less, a length of 40 mm or less, and a motor output of 20 W to 40 W to an outer diameter of 40 mm or less, a length of 80 mm or less, and a motor output of 100 W to 1,000 W.

[0026] When comparing this invention with previous motors that use sintered Nd magnets, the biggest difference is that while the Nd sintered magnet type has a rotation limit of 100,000 RPM, this invention can rotate at 160,000 to 240,000 RPM, and has the potential to be 50% smaller and lighter. This is because sintered magnets have problems with large iron losses (overcurrent loss and hysteresis loss) and heat generation that deteriorates their magnetic properties, but with bonded magnets, each magnetic particle is insulated by the binder resin, which is an insulator, so the iron loss that occurs is very small.

[0027] Furthermore, the problem of rare earth bonded magnets having inferior magnetic force compared to Nd sintered magnets was solved by increasing the rotation speed to over 160,000 RPM and the number of magnetic poles to over four, as well as by reducing the gap with the stator to 0.3 mm or less and devising a magnetic circuit that magnetizes the magnetic poles pseudo-anisotropically. As a result of these comprehensive measures, it was discovered that the overall motor could be made more compact and lightweight by over 50%.

[0028] In terms of rotor processing costs, previous methods using sintered Nd magnets were very expensive, requiring processing of the rotor body which holds the storage space for the sintered Nd magnets, as well as an assembly process for attaching and gluing the sintered magnets, and a process for adjusting the coaxiality.

[0029] The rotor body of the present invention can be manufactured inexpensively by cutting or pressing a round bar, and the rotor is completed simply by integrally molding an injection-molded rare earth magnet into it, an extremely simple process that allows for a significant cost reduction of about 1 / 5 of the manufacturing cost.

[0030] At the same time, because only a thin magnet is formed on the surface, the amount of neodymium magnet used is reduced to about one-fourth of that used in Maxson's motors. Furthermore, when sintered neodymium magnets are machined into a cylindrical shape, waste is generated, resulting in the wasting of scarce and expensive rare earth elements. Injection-molded magnets use magnet powder, resulting in an excellent yield of nearly 100%, making it possible to avoid wasting neodymium resources.

[0031] The SPM motor of the present invention comprises the above-mentioned rotor and a stator having coils arranged axially symmetrically on the outer periphery of the rotor and a yoke that forms a magnetic circuit on the outer periphery of the coils. The electromagnetic coil may optionally include teeth within the yoke coil or may be toothless.

[0032] SPM motors basically generate rotational force (magnetic torque) based on the attractive and repulsive forces generated by the magnetic poles formed by the permanent magnets attached to the rotor and the rotating magnetic field formed around the rotor by the stator.The rotational speed of an SPM motor can be controlled by the frequency of the rotating magnetic field, which can be controlled by the excitation frequency, so SPM motors are not affected by the load and have excellent controllability.

[0033] The manufacturing method for pseudo-polar anisotropic magnetization of magnetic poles is to manufacture an anisotropic magnetization type injection molding die. The injection molding conditions are die temperature and injection temperature 100-150°C, molding pressure 50-150°C. 0MPa, injection speed: 50~150cm 3 / s. Here, the aligning magnetic field is 1 T or more. Furthermore, a polar anisotropic magnetic field of 1 T or more is applied to the ring magnet part, During injection molding Magnetic material Pseudopolar anisotropy At the same time as orienting the material, it is magnetized to saturation.

[0034] Normally, a magnetic field of 3 T is required to saturate magnetize an anisotropic bonded magnet, but because the injection molding temperature is over 100°C, the coercive force of the magnet decreases to below 0.7 T, allowing the magnetic powder to be saturate magnetized with a magnetic field strength of 1 T, and the saturated magnetized magnetic powder can be oriented along the magnetic flux lines. Moreover, because the magnetic powder is saturated magnetized, the saturated state is maintained when the temperature drops, making it possible to produce a saturated magnetized pseudopolar anisotropic magnet. This means that the magnetization process of injection molding can be omitted. [Effects of the Invention]

[0035] This invention can reduce the size and weight of general-purpose small SPM motors by 50%, while also reducing the manufacturing cost of the rotor to about one-fifth. [Brief explanation of the drawings]

[0036] [Figure 1] 1 is a cross-sectional view of an SPM motor according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a four-pole magnet attached to a rotor of the present invention as viewed from the axial direction. [Figure 3] FIG. 2 is a cross-sectional side view of the rotor of the present invention. [Figure 4] 1 is a cross-sectional view of a rotor having a recess made of a magnetic material used in the present invention. [Figure 5] (5a) shows uniaxial anisotropy, and (5b) shows a waveform that is not sinusoidal due to the difference in surface magnetic flux density between the north and south poles, in a laminated rotor made of uniaxially anisotropic stainless steel magnets. [Figure 6] 6A and 6B are diagrams showing waveforms that are radially isotropic and sinusoidal, respectively, in a rotor made of a magnetic material having radially isotropic magnetic properties according to the present invention. [Figure 7] This is a comparison of the appearance of an existing SPM motor product and the present invention. [Figure 8] This is a plan view showing the magnetic field and north and south poles of a conventional ring-shaped polar anisotropic bonded magnet. [Figure 9](a) Cross-sectional view of a magnet and (b) perspective view of a magnet as seen from the axial direction of a sintered Nd type rotor. [Figure 10] This is a cross-sectional view of a Nd sintered type rotor seen from the side. [Figure 11] This is a comparison of the appearance of both motors when the brush motor is made 75% smaller and lighter. BEST MODE FOR CARRYING OUT THE INVENTION

[0037] Brushless SPM motors are the rotor comprises a cylindrical rotor body, a ring magnet fixed to an outer surface of the rotor body, and a rotating shaft fixed to a cylindrical central axis, The rotor body is made of a magnetic material having magnetically isotropic magnetic properties in the radial direction, and has a wavy or knurled unevenness on the outer periphery and fine jagged unevenness of 0.5 to 10 μm, and has a resin layer of a metal adhesive thereon; The ring magnet is an injection-molded rare earth anisotropic bonded magnet with a maximum energy product of 10 to 25 MGOe or more, and is arc-shaped and fixed to the outer periphery of the rotor body. The ring magnet has an even number of magnetic poles (four or more) with N and S poles arranged alternately. The magnetic poles of the rare earth anisotropic bonded magnet are magnetized axially symmetrically with pseudopolar anisotropy, and the magnetic flux distribution density on the surface has a sinusoidal characteristic, The rotor has an outer diameter of 40 mm or less and a length of 60 mm or less. The gap between the rotor and the stator is 0.3 mm or less, The rotor rotates at a rotational speed of 160,000 RPM or more, and the brushless SPM motor has an output of 40W to 1000W.

[0038] In addition, the brushless SPM motor the rotor comprises a cylindrical rotor body, a ring magnet fixed to an outer surface of the rotor body, and a rotating shaft fixed to a cylindrical central axis, The rotor body is made of a magnetic material having magnetically isotropic magnetic properties in the radial direction, has grooves on the outer periphery that are axially symmetrically extended and have the same number of grooves as the number of magnetic poles, and has wave-shaped or knurled irregularities and jagged fine irregularities of 0.5 to 10 μm on the upper part of the grooves, and has a resin layer of metal adhesive thereon; The ring magnet is an injection-molded rare earth anisotropic bonded magnet with a maximum energy product of 10 to 25 MGOe or more, and is arc-shaped and fixed to the outer periphery of the rotor body. The ring magnet has an even number of magnetic poles (four or more) with N and S poles arranged alternately. The magnetic poles of the rare earth anisotropic bonded magnet are magnetized axially symmetrically with pseudopolar anisotropy, and the magnetic flux distribution density on the surface has a sinusoidal characteristic, The rotor has an outer diameter of 40 mm or less and a length of 60 mm or less. The gap between the rotor and the stator is 0.3 mm or less, The rotor rotates at a rotational speed of 160,000 RPM or more, and the brushless SPM motor has an output of 40W to 1000W.

[0039] The manufacturing method for the rotor of a brushless SPM motor is as follows: (1) preparing a round bar of a magnetic material having magnetic properties in the radial direction; (2) The round bar is heat-treated and then machined or pressed into a cylindrical part. (3) forming grooves on the outer periphery of the cylindrical part, the number of which is equal to the number of magnetic poles extending axially symmetrically; (4) subjecting the surface of the cylindrical part on which the groove is formed to a corrugated or knurled processing; (5) Wave-shaped surfaceAlternatively, shot blasting is used to create fine jagged irregularities of 0.5 to 10 μm on the knurled surface, (6) For injection molding of rare earth anisotropic bonded magnets, an anisotropic magnetized injection mold is prepared, and the mold temperature and injection temperature are set to 100-150°C, the molding pressure to 50-150MPa, and the injection speed to 50-150cm. 3 / sec, and a polar anisotropic magnetic field of 1 T or more is applied to the formed ring magnet portion to orient the magnetic material pseudopolar anisotropically during injection molding and simultaneously magnetize it pseudopolar anisotropically to saturation; (7) Then, remove from the injection mold. It is characterized by:

[0040] In addition, the manufacturing method of the rotor of the SPM motor is as follows: (5) The next step is (5-1) Forming a resin layer on the fine irregularities using a metal adhesive; It is characterized by:

[0041] A detailed description will be given below with reference to FIGS. <Brushless SPM motor> As shown in FIG. 1, the brushless SPM motor 1 comprises a rotor 2, a stator 3, and a rotating shaft. It consists of 4. The rotor 2 will be described below.

[0042] <Rotor> As shown in FIGS. 2 and 3, the rotor 2 is made up of a rotor body 21, rare earth anisotropic bonded magnets 22 (22N, 22S), and a rotating shaft 23.

[0043] <Rotor body> The rotor body 21 is made of a magnetic material with radially isotropic magnetic properties and is cylindrical in shape with a hole in the center for attaching the rotating shaft. This allows the magnetic field distribution generated by all four or more magnetic poles to be the same when they are pseudo-anisotropically magnetized.

[0044] As shown in Figure 4, the outer periphery has four or more grooves (concave portions) extending axially symmetrically. The number of grooves is the same as the number of magnetic poles. The outer periphery of the rotor body has corrugated or knurled irregularities and fine jagged irregularities of 0.5 to 10 μm, on top of which a resin layer is formed using a metal adhesive. This processing of the outer periphery is intended to firmly fix the ring magnet to the outer periphery of the rotor body.

[0045] Furthermore, the magnetic poles utilize the large magnetic force acting between the magnet body and the magnetic material by integrally magnetizing them with pseudopolar anisotropy, strengthening the bonding force between them. These measures were found to avoid the centrifugal force problem. In other words, high-speed rotation was made possible without installing a non-magnetic shatterproof case on the surface of the ring magnet.

[0046] To manufacture the rotor body, a round bar of magnetic material is heat-treated and then machined or pressed to the required cylindrical shape. The circumferential surface is then polished, and grooves are machined in the same number as the number of poles. The groove depth and width should be no more than one-third the thickness of the magnet. The surface is then corrugated or knurled, and then shot-blasted to create fine jagged irregularities of 0.5 to 10 μm. A resin layer is then formed on top of this using a metal adhesive. This surface treatment increases the bonding strength between the magnet and rotor surface.

[0047] The radius of the rotor is preferably within ±0.010 mm in order to keep the gap between the rotor and the stator at 0.3 mm or less.

[0048] <Rare earth anisotropic bonded magnet> It is preferable that the injection molded rare earth anisotropic bonded magnet (magnetically anisotropic rare earth bonded magnet) has as high a maximum energy product as possible, but the present invention can be realized by using one having 10 MGOe to 25 MGOe. Although the magnetic performance is significantly inferior to that of sintered Nd magnets with a maximum energy product of 40 MGOe or more, the number of magnetic poles on the rotor surface magnet is at least four, which are magnetized alternately to north and south poles, and the magnetic material is magnetized pseudopolar anisotropically to saturation.

[0049] Moreover, these magnets are formed using the injection molding process, resulting in extremely high dimensional precision, and are arranged symmetrically around the central axis of rotation of the main body, allowing the gap between the stator and rotor to be controlled to 0.3 mm or less.The magnets are also magnetized with pseudopolar anisotropy, resulting in a small demagnetizing field and enabling a relatively large magnetic flux to be drawn out.

[0050] As a result, although the performance of the magnet itself is inferior to that of a sintered neodymium magnet, it is able to draw out the same or greater amount of magnetic flux as a motor's magnetic circuit.

[0051] If the magnetic material has uniaxial anisotropy in cross section, such as a laminated plate of stainless steel magnet, and is magnetized with pseudopolar anisotropy, the magnetic field distribution emitted from the four poles will be different, as shown in Figure 5. However, as shown in Figure 6, this invention uses a magnetic material that is isotropic in the radial direction, so the magnetic field distribution emitted by the four poles will be the same. This is important in reducing cogging in the motor.

[0052] <Magnetic shape and size> The specific shape and size of the magnet, that is, the outer diameter, thickness, and length of the magnet, are adjusted appropriately according to the basic specifications of the SPM motor, such as its output and motor size, while also taking into account its rotation speed and centrifugal force. The motor output ranges from 100W to 1000W, but can be realized with a rotor diameter of 8mm to 32mm, an inner diameter of 5mm to 20mm, a length of 5mm to 20mm, and a magnet usage of 0.8g to 6g.

[0053] <Joint strength between magnet and rotor body> Regarding the bonding strength between the magnet and rotor body against centrifugal force, it is necessary to strengthen both the bonding strength of the adhesive and the magnetic bonding force due to pseudopolar anisotropic magnetization, taking into consideration the motor output and rotation speed. If a stronger bonding force is required, the outer surface of the rotor body is shot blasted to a roughness of 0.5 μm to 5 μm, a metal adhesive is applied on top, and the rotor surface is covered with resin, which is then bonded to the resin of the injection-molded magnet, ensuring a strong bond.

[0054] Furthermore, if it is necessary to strengthen the bond strength in consideration of centrifugal force, it is possible to increase the bond strength by applying a corrugated or knurled finish to the outer surface of the rotor body, thereby increasing the bond surface area with the magnet.

[0055] Regarding the bonding strength of the surface magnet, whether or not it will break depends on the shape, weight, uniformity of the magnetic properties of the magnet, the coaxiality of the rotor, bonding strength, etc., so we actually installed a rotational speed testing machine of 200,000 rpm to evaluate it and confirmed that the ring magnet would not break.

[0056] <Cost> The cost consists of the cost of manufacturing the rotor body from magnetic material, the cost of fitting the rotating shaft into the hole in the center of the rotor body, and the cost of forming the rare earth bonded magnet on the outer periphery using an injection process. Because there are no costly parts with complex structures, no precision assembly process is required, the magnetization process can be omitted, and the amount of expensive rare earth used is small at 4g or less, it is thought that the rotor can be manufactured at a manufacturing cost of less than one-fifth of the manufacturing cost of conventional rotor products.

[0057] <Motor specifications> The output is 100W to 1000W, the rotor speed is 160,000 RPM or more, the magnet weight is 4g or less, the number of magnetic poles is 4 or more, and the number of electromagnets on the stator side is 6 or more. The yoke of the electromagnet on the stator side may or may not have teeth. [Example]

[0058] <First Example> This is an example of a 100W output motor. The rotor body of the brushless SPM motor was made by machining a roughly cylindrical ring part from a round bar of magnetic material.

[0059] The injection-molded anisotropic rare earth bonded magnet is formed in an arc shape around the outer periphery of the rotor body, and has a maximum energy product of 18 MGOe. The conditions for injection molding of rare earth anisotropic bonded magnets are: mold temperature and injection temperature: 130°C, molding pressure: 100 MPa, injection speed: 90 cm 3 A polar anisotropic magnetic field of 1 T or more was applied to the ring magnet portion, and the magnetic material was polar anisotropically oriented during injection molding, and simultaneously magnetized to saturation.

[0060] The rotor's surface magnet has four magnetic poles, and is magnetized with alternating north and south poles at the groove boundary, and is pseudo-polar anisotropically saturated. Moreover, these magnets are formed using the injection molding process, with extremely high dimensional accuracy, and are arranged symmetrically around the main body's central axis of rotation, with a gap of 0.2 mm between the stator and rotor.

[0061] The specific shape and size of the magnets were as follows: rotor diameter 11 mm, inner diameter 7 mm, magnet thickness 2 mm, length 7.5 mm, and magnet amount 1 g.

[0062] The motor's rotation speed is 200,000 RPM, and the strength of the bond between the magnet and rotor body against centrifugal force is determined by taking into consideration the motor output and rotation speed. The outer surface of the rotor body is knurled and then shot blasted to an average roughness of 3 μm, and then a metal adhesive is applied on top of that, and the rotor surface is covered with resin, and then Injection Molded Magnets The resins are bonded together, ensuring a high bond strength.

[0063] The bonding strength of the surface magnets was evaluated using a rotational speed tester that could rotate at 200,000 revolutions per minute. All ten rotors used in the experiment passed the test without breaking at 200,000 revolutions.

[0064] In terms of cost, it costs 30 yen to manufacture the rotor body from magnetic material, 40 yen to fit the rotating shaft into the hole in the center of the rotor body, and 80 yen to form the rare earth bonded magnet on the outer periphery using an injection process, and the amount of expensive rare earth used is 1.1 g, which costs 50 yen, for a total of 200 yen, which is thought to be about 1 / 10 of the estimated manufacturing cost of 2,000 yen for a rotor of a conventional product.

[0065] The motor specifications of the present invention are: output 100W, motor size 18mm diameter, 30mm length, weight 50g, rotor rotation speed 200,000 RPM, magnet weight less than 1g, number of magnetic poles 4, number of electromagnets on the stator side 6. The yoke of the electromagnet on the stator side does not have teeth.

[0066] Maxon's 100W motor has a diameter of 19mm, a length of 30mm, a weight of 100g, a rotor speed of 60,000 RPM, a magnet weight of 4.3g, two magnetic poles, and three electromagnets on the stator side. It can be seen that the invention has achieved a 50% reduction in size and weight, and has succeeded in significantly reducing costs. [Industrial Applicability]

[0067] The use of small motors for robots is rapidly increasing, but at the same time, there is a demand for smaller, lighter, and cheaper motors. This invention makes it possible to reduce the size and weight of conventional motors by 50% and also significantly reduce manufacturing costs, and is expected to be widely applied to various robots in the future. [Explanation of symbols]

[0068] 1: Brushless SPM motor 2: Rotor 21: Rotor body 22: Rare earth anisotropic bonded magnet (rare earth bonded magnet, magnet) 22N: North pole of rare earth bonded magnet 22S: South pole of rare earth bonded magnet 23: Rotation axis 24: Groove (recess) 3: Stator 4: Rotation axis 5: Magnetic field distribution of a rotor made of uniaxially anisotropic stainless steel magnet 51: Uniaxial anisotropy 52: Magnetic flux flow 6: Magnetic field distribution in isotropic magnetic materials 61: Isotropic 7: Polar anisotropic magnetization pattern of the magnet in Patent Document 1 8: Rotor made of sintered neodymium magnet 81: Case 82: Sintered magnet 82N: North pole of sintered magnet 82S: S pole of sintered magnet 83: Shaft

Claims

1. A brushless SPM motor consisting of a stator and a rotor, the rotor comprises a cylindrical rotor body, a ring magnet fixed to an outer surface of the rotor body, and a rotating shaft fixed to a cylindrical central axis, The rotor body is made of a magnetic material having magnetically isotropic magnetic properties in the radial direction, and has a wavy or knurled irregularity on the outer periphery and a fine jagged irregularity of 0.5 to 10 μm, and has a resin layer of a metal adhesive thereon; The ring magnet is an injection-molded rare earth anisotropic bonded magnet having a maximum energy product of 10 to 25 MGOe or more and arc-shaped on the outer circumferential surface of the rotor body, and is fixed to the periphery of the magnetic material, and has magnetic poles consisting of an even number of four or more poles with N poles and S poles arranged alternately, The magnetic poles of the rare earth anisotropic bonded magnet are magnetized axially symmetrically with pseudopolar anisotropy, and the magnetic flux distribution density on the surface has a sinusoidal characteristic, The rotor has an outer diameter of 40 mm or less and a length of 60 mm or less. The gap between the rotor and the stator is 0.3 mm or less, The rotor rotates at a rotational speed of 160,000 RPM or more, and the brushless SPM motor has an output of 40W to 1000W.

2. A brushless SPM motor consisting of a stator and a rotor, the rotor comprises a cylindrical rotor body, a ring magnet fixed to an outer surface of the rotor body, and a rotating shaft fixed to a cylindrical central axis, The rotor body is made of a magnetic material having magnetically isotropic magnetic properties in the radial direction, has grooves on the outer periphery extending axially symmetrically in the same number as the number of magnetic poles, and has corrugated or knurled irregularities and jagged fine irregularities of 0.5 to 10 μm on the upper part of the grooves, and has a resin layer of a metal adhesive thereon; The ring magnet is an injection-molded rare earth anisotropic bonded magnet having a maximum energy product of 10 to 25 MGOe or more and arc-shaped on the outer circumferential surface of the rotor body, and is fixed to the periphery of the magnetic material, and has magnetic poles consisting of an even number of four or more poles with N poles and S poles arranged alternately, The magnetic poles of the rare earth anisotropic bonded magnet are magnetized axially symmetrically with pseudopolar anisotropy, and the magnetic flux distribution density on the surface has a sinusoidal characteristic, The rotor has an outer diameter of 40 mm or less and a length of 60 mm or less. The gap between the rotor and the stator is 0.3 mm or less, The rotor rotates at a rotational speed of 160,000 RPM or more, and the brushless SPM motor has an output of 40W to 1000W.

3. A method for manufacturing a rotor of a brushless SPM motor comprising a stator and a rotor, (1) preparing a round bar of a magnetic material having magnetic properties in the radial direction; (2) The round bar is subjected to heat treatment and then machined or pressed into a cylindrical part; (3) forming grooves on the outer periphery of the cylindrical part, the number of which is equal to the number of magnetic poles extending axially symmetrically; (4) subjecting the surface of the cylindrical part on which the groove is formed to a corrugated or knurled processing; (5) Forming fine jagged irregularities of 0.5 to 10 μm on the surface of the corrugated or knurled surface by shot blasting; (6) For injection molding of rare earth anisotropic bonded magnets, an anisotropic magnetized injection mold is prepared, and the mold temperature and injection temperature are set to 100-150°C, the molding pressure to 50-150 MPa, and the injection speed to 50-150 cm ３ / sec, and a polar anisotropic magnetic field of 1 T or more is applied to the ring magnet portion to be formed, so that the magnetic material is pseudopolar anisotropically oriented and simultaneously pseudopolar anisotropically magnetized to saturation during injection molding; (7) Then, remove from the injection mold. A method for manufacturing a rotor comprising the steps of:

4. In claim 3, in the step following (5), (5-1) Forming a resin layer on the fine irregularities using a metal adhesive; A method for manufacturing a rotor comprising the steps of:

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