Surface magnetic type synchronous machine, rotator of the same, and method for producing rotator

Abstract

To achieve high-speed rotation and increased output of a motor using a rare earth anisotropic bond magnet.SOLUTION: A rotator 22 of a brushless SPW motor is formed from a ring magnet having a maximum energy product of 10 MGOe or more and a cylindrical stainless magnet, wherein the ring magnet is magnetized with four or more magnetic poles, in which N poles and S poles are alternately arranged, with pseudopolar anisotropy via magnetic materials or a stainless magnet, by injection molding of a rare earth anisotropic bond magnet, and the ring magnet is fixed to the outer peripheral part of the rotator main unit with bonding strength by magnetic bonding force and a metal adhesive to enhance resistance to centrifugal force.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] There are various types of electric motors (including generators, simply called "motors"). Recently, with the development of inverter control and the widespread use of rare earth magnets with high magnetic properties, brushless motors, which are energy-saving, highly efficient, and capable of high torque or output, have been attracting attention.

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

[0004] For small robot motors that require excellent controllability, products made by Maxon of Switzerland are widely used, but there is a demand for motors that are at least 50% smaller, lighter, have higher output, and are less expensive. To achieve this, efforts have been made to reduce size, weight, and output by increasing rotation speed, and motors with rotation speeds of 60,000 to 100,000 RPM have been successfully developed recently. However, attempts to increase rotation speeds even further have run into the problem of heat generation in the sintered Nd magnets used, and the development of SPM motors with rotation speeds of 120,000 RPM or more faces a major technical hurdle.

[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 magnet powder, which has a better aligning magnetic field than Nd-Fe-B 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 N poles and S poles, and each magnetic pole is magnetized with polar anisotropy without the use of a magnetic material, as shown in Figure 6. However, the invention disclosed in Patent Document 1 had the drawback that the magnetic force was weak and the ring magnet would be damaged due to the centrifugal force at rotation speeds of 120,000 RPM or more.

[0006] By adopting an injection-molded pseudopolar anisotropic rare earth bonded magnet, the present invention solves the heat generation problem of Maxon's sintered neodymium magnets and the centrifugal force problem of the invention in Patent Document 1, thereby achieving a size and weight reduction of more than 50% compared to current products. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2000-195714 A Summary of the Invention [Problem to be solved by the invention]

[0008] The standard product for small robot motors that are widely used is that of Maxon. To obtain a large force, a two-pole magnetized neodymium sintered magnet is attached to the inside of the rotor, and it is used for 60,000 to 100,000 revolutions to realize a small, high-output motor (Fig. 7, Fig. 8). Any attempt to increase the speed and improve performance beyond this is difficult due to the problem of heat generation in the neodymium sintered magnet.

[0009] Although rare earth anisotropic bonded magnets do not generate heat even when rotating at high speeds, their magnetic force is small, so it is difficult to replace them with sintered Nd magnets and reduce their size even if the rotation speed is doubled. Furthermore, if there is non-uniformity in the coaxiality of the rotor's shape or weight balance, or in the coaxiality of the magnetic field created by the magnets, cogging torque and vibration are likely to occur.

[0010] High speed rotation creates a large centrifugal force that acts on the magnets attached to the surface, but if there is non-uniformity in the coaxiality, stress will concentrate in certain areas, causing peeling to begin from those areas, which will then cause fatigue failure of the ring magnet. Even if we simply replace the existing magnets with rare earth bonded magnets that do not generate heat, this alone will not be enough to design a high speed motor.

[0011] The inventors have a track record of successfully reducing the size and weight of a small brush motor by 75% by increasing the number of magnetic poles from 2 to 4 and doubling the rotation speed from the conventional 3000 RPM to 6000 RPM (Fig. 9). In addition, they have achieved smooth rotation by changing the 2-pole radially oriented ferrite magnet to a compression molded rare earth ring magnet, magnetizing it anisotropically, and making the generated magnetic field distribution a sine waveform. 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.

[0012] This experience suggests that even if sintered Nd magnets are replaced with rare earth anisotropic bonded magnets, in other words, by replacing magnets with inferior performance, and the amount of magnet energy used is reduced to half, if an eight-fold improvement in performance can be achieved through the structural design of the motor, it is entirely possible to make the motor 50% smaller and lighter.

[0013] The present invention was made in consideration of these circumstances, and was developed based on the idea that by using injection-molded rare earth magnets and magnetizing them with pseudo polar 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 poles to reduce the magnetic force of the magnet and increase the motor rotation speed to over 120,000 RPM, a 50% reduction in size and weight can be achieved, and that pseudo polar anisotropic magnetization via magnetic material could solve the centrifugal force problem. Here, pseudopolar anisotropy refers to an orientation in which the magnetic poles of the ring magnet and the magnetic material are integrated and saturated with polar anisotropy, strongly bonding the ring magnet with the magnetic material of the rotor, which has the effect of generating a force that counteracts centrifugal force, while at the same time causing the magnetic field emitted from the ring magnet to have a sinusoidal waveform, enabling smooth rotation (Figure 4). [Means for solving the problem]

[0014] The inventors first considered the importance of enabling high-speed rotation of over 120,000 RPM, and 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 part is attached to a precision mold for injection molding, 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.

[0015] Moreover, in terms of magnetism, we were able to realize a pseudopolar anisotropic orientation, which resulted in a highly coaxial sinusoidal magnetic field distribution. This reduced the motor's cogging torque, suppressed vibration generation, and reduced stress concentration between the magnet and magnetic material during rotation. To achieve this, we decided to design and prototype a pseudopolar anisotropic mold to be used during injection molding.

[0016] Next, the number of magnetic poles was increased from two to four and then six to compensate for the decrease in magnetic force.Furthermore, the gap between the outer periphery of the rotor magnet and the inner periphery of the stator electromagnet was reduced from approximately 1.5 mm (Maxon's conventional product) to 0.5 mm or less.This was only possible thanks to the excellent concentricity of the rotor.

[0017] As described above, by combining the following factors - the use of injection-molded rare earth anisotropic bonded magnets, making the magnetic poles anisotropic, increasing the number of magnetic poles from two to four or more, reducing the gap between the rotor and stator to 0.5 mm or less, and increasing the rotor speed to 120,000 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%.

[0018] The biggest problem in the design was whether the ring magnet could withstand the large centrifugal force and whether the adhesive strength between the ring magnet and the rotor body parts could withstand it. Even a slight misalignment in coaxiality or vibration during motor rotation would create stress concentration points at specific points on the joint surface between the magnet and rotor, causing cracks to form from those points and leading to damage to the ring magnet. A common countermeasure is to attach a non-magnetic shatterproof cover to the surface of the ring magnet and apply pressure from the outside to prevent damage due to centrifugal force, but this increases the gap between the magnet and the stator, making it impossible to achieve sufficient miniaturization.

[0019] The present invention relates to Next, the joining strength was improved by increasing the unevenness of the rotor body and using a metal adhesive. The joining strength was also improved by making the surface corrugated to increase the bonding area. Furthermore, stress concentration was suppressed by improving the coaxiality of the rotor and magnetizing the magnetic poles with pseudopolar anisotropy to create a smooth magnetic field distribution with high coaxiality.The greatest feature of this design is that it enables high speed rotation without installing a non-magnetic case on the surface of the ring magnet. In other words, the resistance to centrifugal force is maintained by the strength of the adhesive and the magnetic force acting between the pseudopolar anisotropically magnetized magnet and the magnetic body.

[0020] In addition to the above measures, because centrifugal force is proportional to the radius of rotation, in the present invention, the rotor diameter is set to an outer diameter of 12 mm or less and the length to 15 mm or less to prevent damage to the ring magnet.

[0021] The rotor body is made of a magnetic material, but by changing to a stainless steel magnet, it was found that the magnetic flux emanating from the magnetic poles increased by 10%. In addition, the resistivity of the stainless steel magnet is 72μΩcm, more than twice that of the magnetic material (32μΩcm), reducing eddy currents and heat generated during high-speed rotation. This strengthens the magnetic coupling force acting between the magnet and the stainless steel magnet of the rotor, making it possible to increase motor output or further reduce the size and weight.

[0022] When comparing the present 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, the present invention can rotate at 120,000 to 200,000 RPM, and has the potential to be 50% smaller and lighter. This is because sintered magnets have problems with large iron losses (eddy current losses and hysteresis losses) and heat generation that deteriorates the magnetic properties, but with bonded magnets, each magnetic particle is insulated by the binder resin, which is an insulator, so the iron loss and heat generation are extremely small. Furthermore, regarding the issue of rare earth anisotropic bonded magnets having inferior magnetic force compared to Nd sintered magnets, it was discovered that by devising a magnetic circuit that could achieve eight times the performance per unit magnet energy, it would be possible to reduce the size and weight of the motor body by more than 50%.

[0023] In terms of rotor processing costs, the previous method using sintered Nd magnets was extremely expensive, requiring processing of the rotor body which contains the storage space for the Nd sintered magnets, an assembly process for mounting and gluing the sintered magnets, and a process for adjusting the coaxiality. The injection molding type of the present invention has a high yield rate of Nd bonded magnets, and the rotor body only needs to be processed into a cylindrical shape. The rotor is completed simply by molding this into a single piece with the magnet, which is an extremely simple process that makes it possible to significantly reduce manufacturing costs to about 1 / 5.

[0024] At the same time, because only a thin magnet is formed on the surface, the amount of Nd magnet used is reduced to about one-quarter. Also, when machining sintered Nd magnets into a cylinder, machining waste is generated, resulting in the waste of scarce and expensive rare earth elements. Injection-molded magnets use magnet powder, so the yield is extremely high at nearly 100%, making it possible to avoid wasting Nd resources.

[0025] The SPM motor of the present invention comprises the above-mentioned rotor, and a stator having coils evenly arranged around the rotor and a yoke that constitutes a magnetic circuit on the outer periphery of the coils. The electromagnetic coil may optionally include teeth within the yoke coil or may have no teeth.

[0026] Synchronous machines 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 rotation 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.

[0027] The manufacturing method for pseudo-polar anisotropic magnetization of magnetic poles is to manufacture anisotropic magnetization type injection molding die poles. The injection molding conditions are mold temperature and injection temperature 100 to 150°C, molding pressure 50 to 150 MPa, injection speed: 50 to 150 cm 3 / s. Here, the aligning magnetic field is set to 1 T or more. Normally, a magnetic field of 3 T is required to saturate magnetize a rare earth anisotropic bonded magnet, but because the injection molding temperature is over 100°C, the coercive force of the magnet decreases to 0.7 T or less, and the magnetic powder can be saturate magnetized with a magnetic field strength of 1 T, and the magnet can be oriented along the magnetic flux lines. Moreover, since the magnetic powder is saturated and magnetized, the saturated magnetized state is maintained when the temperature drops to room temperature, making it possible to produce a saturated magnetized pseudopolar anisotropic magnet, which means that the magnetization step in the injection molding process can be omitted. Effect of the Invention

[0028] This invention can reduce the size and weight of general-purpose small SPM motors by 50%, while reducing the manufacturing cost of the rotor to about 1 / 5. [Brief description of the drawings]

[0029] [Figure 1] 1 is a cross-sectional view of an SPM motor according to a first embodiment of the present invention. [Diagram 2] 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. [Diagram 3]FIG. 2 is a cross-sectional side view of the rotor of the present invention. [Figure 4] FIG. 2 is a plan view showing the magnetic field and north and south poles of a ring-shaped pseudopolar anisotropic bonded magnet of the present invention. [Diagram 5] Photographs comparing the appearance of an existing SPM motor product and the present invention. [Figure 6] This is a plan view showing the magnetic field and north and south poles of a conventional ring-shaped polar anisotropic bonded magnet. [Figure 7] (a) Cross-sectional view of a magnet and (b) a perspective view of a magnet as viewed from the axial direction of a neodymium sintered type rotor. [Figure 8] This is a cross-sectional view of a Nd sintered type rotor as seen from the side. [Figure 9] This is a comparison of the appearance of both motors when the brush motor is 75% smaller and lighter. BEST MODE FOR CARRYING OUT THEINVENTION

[0030] Brushless SPM motors are In a brushless SPM motor consisting of a stator and a rotor, The rotor is provided with a ring magnet and a cylindrical magnetic material (hereinafter referred to as the magnetic material, etc.) that is circumscribed on the rotating shaft. The ring magnet is an injection-molded rare earth anisotropic bonded magnet with a maximum energy product of 10 MGOe or more, and is fixed to the outside of the magnetic material, etc., and has magnetic poles consisting of an even number of four or more poles arranged alternately with N poles and S poles, and each magnetic pole is magnetized with pseudopolar anisotropy via the magnetic material, The rotor has a shape and size of an outer diameter of 20 mm or less and a length of 40 mm or less, The gap between the rotor and the stator is 0.5 mm or less. The rotor rotates at a rotational speed of 120,000 RPM or more, and the brushless SPM motor has an output of 20W to 400W.

[0031] In addition, the brushless SPM motor: The degree of unevenness of the outer periphery of the rotor is 0.5 to 10 μm, and a resin layer is formed on top of it with a metal adhesive to firmly fix the ring magnet and the outer periphery of the magnetic material.

[0032] In addition, the brushless SPM motor: The cylindrical magnetic material of the rotor is a stainless steel magnet.

[0033] The manufacturing method for the rotor of a brushless SPM motor is as follows: The conditions for injection molding of rare earth anisotropic bonded magnets are: mold temperature and injection temperature: 100-150°C, molding pressure: 50-150MPa, injection speed: 50-150cm 3 / sec.

[0034] A detailed explanation will be given below with reference to Figs. 1 to 5. <Brushless SPM motor> As shown in FIG. 1, the brushless SPM motor 1 is composed of a rotor 2, a stator 3, and a rotating shaft 4. The rotor 2 will now be described.

[0035] <Rotor> As shown in FIGS. 2 and 3, the rotor 2 is made up of a shaft 21, a rotor body 22, and bonded magnets 23 (23N, 23S). The rotor body 22 is made of a magnetic material or a stainless steel magnet. As a magnetic material, a cylindrical ring part is preferable, which is punched out of a thin sheet of Si steel into a disk shape, and laminated with insulating coating on both sides. As a stainless steel magnet, any material is acceptable, but it is preferable to use an iron-based material such as Cr-Ni stainless steel or Mn non-magnetic steel, which is in a non-magnetic austenite phase at room temperature and becomes a magnetic martensite phase after cold working, and exhibits semi-hard magnetic properties. The shape is usually a laminate of thin sheets with insulating coating on both sides.

[0036] Stainless steel magnets are made by changing the structure of Ni-based stainless steel from 100% austenite to one containing 80% or more martensite, making it into a semi-hard magnetic material, and then saturating magnetizing it to make a permanent magnet. Their magnetic performance at room temperature is as follows: saturation magnetization of 12,000 to 16,000 G, coercive force of 80 to 300 Oe, residual magnetism Br of 6,000 to 8,000 G, and maximum energy product of 0.2 to 4 MGOe.

[0037] It is preferable for injection-molded rare earth anisotropic bonded magnets to have the highest possible maximum energy product, but the present invention can be realized by using magnets with 10MGOe to 25MGOe. Although the magnetic performance is significantly inferior to that of Nd sintered magnets with a maximum energy product of 40MGOe or more, the number of magnetic poles on the rotor's surface magnet is at least four, which are magnetized alternately with N and S poles, and are saturated magnetized with pseudopolar anisotropy via magnetic material or stainless steel magnets (Figure 4).

[0038] Moreover, these magnets are formed by injection molding, and not only do they have excellent dimensional precision, but they are also arranged symmetrically around the central axis of rotation of the main body, making it possible to control the gap between the stator and rotor to 0.5 mm or less. In addition, the magnets are magnetized with pseudopolar anisotropy, which means that the demagnetizing field is small and a relatively large magnetic flux can be drawn out. 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.

[0039] The specific shape and size of the magnet, that is, the outer diameter, thickness and length of the magnet, are adjusted as appropriate according to basic specifications such as the output and size of the SPM motor, while also taking into account its rotation speed and centrifugal force. The motor output is from 40W to 400W, but the rotor diameter is 8mm to 16mm, the inner diameter is 6mm to 12mm, the length is 5mm to 20mm, and the magnet weight is 0.8g to 4g or less.

[0040] Regarding the bonding strength between the magnet and the rotor body against centrifugal force, it is necessary to further strengthen both the bonding strength of the adhesive and the magnetic bonding force due to the pseudo polar anisotropic raw magnetization, taking into account the motor output and rotation speed. If a greater bonding strength of the adhesive is required, the outer circumferential 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 of that, and the rotor surface is covered with resin, which is then bonded to the resin of the injection molded magnet, thereby ensuring a great bonding strength.

[0041] Furthermore, if it is necessary to strengthen the joint strength in consideration of centrifugal force, it is possible to increase the joint strength by applying a corrugated finish to the outer surface of the rotor, thereby increasing the joint surface area with the magnet.

[0042] Regarding the bonding strength of the surface magnet, whether it will break or not depends on the uniformity of the magnet workmanship, the coaxiality of the rotor, the bonding strength, etc., so we actually installed a rotational speed testing machine with a speed of 200,000 RPM to evaluate it and confirmed that the ring magnet would not break.

[0043] The cost consists of the cost of manufacturing the magnetic material or stainless steel magnet of the rotor body in a laminated structure, 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 anisotropic bonded magnet on the outer periphery through an injection process. Because there are no costly parts with complex structures, no need for precision assembly processes, and the magnetization process can be omitted, and because the amount of expensive rare earth used is small at 4g or less, it is thought that the manufacturing cost can be reduced to less than one-fifth of the manufacturing cost of rotors of conventional products.

[0044] <Motor specifications> Output is 40W~400W, rotor speed is 120,000~200,000 RPM, magnet weight is 4g or less, number of magnetic poles is 4 or more, number of electromagnets on the stator side is 6 or more. The electromagnets on the stator side may have a yoke or may be coreless without a yoke. EXAMPLES

[0045] <First Example> This is an example of a 100W output motor. The rotor body of the brushless SPM motor uses a cylindrical ring component that is punched into a disk shape from a thin sheet of silicon steel as the magnetic material, and is laminated with an insulating coating on both sides.

[0046] The injection-molded magnetically anisotropic rare earth bonded magnets used have a maximum energy product of 18 MGOe. The number of magnetic poles on the rotor's surface magnet is at least four, with alternating N and S poles, and polar anisotropically saturated magnetization. Moreover, these magnets are molded using the injection molding process, with extremely high dimensional accuracy, and are arranged symmetrically around the central axis of rotation of the main body, with a gap between the stator and rotor of 0.4 mm.

[0047] 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 amount of magnet used 1 g.

[0048] The motor's rotation speed is 200,000 RPM, and in order to ensure the strength of the bond between the magnet and the rotor body against centrifugal force, the outer surface of the rotor body is shot blasted to an average roughness of 3 μm, taking into account the motor output and rotation speed, and then a metal adhesive is applied on top of that to cover the surface of the rotor with resin, which is then bonded to the resin of the injection-molded magnet, ensuring great bond strength.

[0049] The bonding strength of the surface magnets was evaluated using a rotational speed test machine that could rotate at 200,000 RPM, and all ten rotors used in the experiment passed the test.

[0050] In terms of cost, it costs 80 yen to manufacture the magnetic material of the rotor body in a laminated structure, 40 yen to attach the rotating shaft to the hole in the center of the rotor body, and 100 yen to form the rare earth anisotropic bonded magnet on the outer periphery through the injection process. Furthermore, the amount of expensive rare earth used is 1.1 g, which costs 80 yen, for a total of 300 yen, which is approximately 1 / 5 of the estimated manufacturing cost of 1,500 yen for a rotor of a conventional product.

[0051] The motor specifications of the present invention are: output 100W, motor size diameter 18mm, length 30mm, weight 50g, rotor speed 200,000 RPM, magnet weight less than 1g, number of magnetic poles 4, number of electromagnets on the stator side 6. The electromagnets on the stator side are coreless with no yoke (Fig. 5).

[0052] Maxon's 100W motor has a motor size of 19mm in diameter, 30mm in length, weighs 100g, has 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.

[0053] <Second Example> The rotor body of the first embodiment is replaced with a stainless steel magnet. This is an example where the motor torque is increased by 10% and the motor output is 110W.

[0054] <Third Example> In the first embodiment, the motor output is 200 W, the rotor diameter is 15 mm, the inner diameter is 9 mm, the magnet thickness is 3 mm, the length is 10 mm, and the magnet usage amount is 2 g. Since the centrifugal force is large, the outer periphery of the rotor body is corrugated to increase the contact area with the magnet. [Industrial Applicability]

[0055] The use of small motors for robots is rapidly increasing, but at the same time, there is a demand for them to be smaller, lighter, and less expensive. This invention makes it possible to reduce the size and weight of conventional products by 50% and also significantly reduce manufacturing costs, and is expected to be used in a wide range of robots in the future. [Explanation of symbols]

[0056] 1: Brushless SPM motor 2: Rotor 21: Rotating shaft, 22: Rotor body, 23N: N pole of rare earth anisotropic bonded magnet, 23S: S pole of rare earth anisotropic bonded magnet 3: Stator 4: Rotation axis 5: Ring-shaped polar anisotropic magnet 6: Nd sintered magnet type rotor 61: shaft, 62: case, 63N: north pole of Nd sintered magnet, 63S: south pole of Nd sintered magnet

Claims

1. In a brushless SPM motor consisting of a stator and a rotor, The rotor is provided with a ring magnet and a cylindrical magnetic material (hereinafter referred to as the magnetic material, etc.) that circumscribes the rotating shaft. The ring magnet is an injection molded rare earth anisotropic bonded magnet having a maximum energy product of 10 MGOe or more, and is fixed to the outside of the magnetic material, etc., and has magnetic poles consisting of an even number of four or more poles arranged alternately with N poles and S poles, and each magnetic pole is magnetized with pseudopolar anisotropy via the magnetic material, The rotor has an outer diameter of 20 mm or less and a length of 40 mm or less. The gap between the rotor and the stator is 0.5 mm or less. The rotor rotates at a rotational speed of 120,000 RPM or more, and the brushless SPM motor has an output of 20W to 400W.

2. 2. The rotor according to claim 1, A brushless SPM motor characterized in that the unevenness of the outer periphery of the rotor is 0.5 to 10 μm, and a resin layer is formed on top of it using a metal adhesive to firmly fix the ring magnet and the outer periphery of the magnetic material.

3. In the rotor of the brushless SPM motor according to claims 1 and 2, A brushless SPM motor, characterized in that the cylindrical magnetic material of the rotor is a stainless steel magnet.

4. In the method for manufacturing a rotor of a brushless SPM motor according to any one of claims 1 to 3, The conditions for injection molding of rare earth anisotropic bonded magnets are: mold temperature and injection temperature: 100 to 150°C, molding pressure: 50 to 150 MPa, injection speed: 50 to 150 cm ３ / sec.

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