Brushless spm motor and manufacturing method of rotor thereof

Abstract

To attain high-speed rotations and an increase of output of a motor using a rare earth anisotropic bond magnet.SOLUTION: A rotor 2 of a brushless SPW motor consists of arcuate magnets 22N and 22S having a maximum energy product of 10 MGOe or more and a non-magnetic part 211 of a protrusion extending from a stainless magnet of a cylinder main body 21 and the cylinder main body in an axial symmetry. In the arcuate magnets, four or more magnetic poles and an N pole / S pole are alternately magnetized in pseudo-polar anisotropy by injection molding of a rare earth anisotropic bond magnet and the arcuate magnet is firmly fixed with an outer peripheral part of a rotor main body by a metal adhesive agent, thereby improving centrifugal force resistance.SELECTED DRAWING: Figure 2

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), 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 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 recently motors with rotation speeds of 60,000 to 100,000 RPM have been successfully developed. However, attempts to achieve even higher rotation speeds face a major technical barrier: the use of sintered Nd 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 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. 8, Fig. 9). 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 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 two to four and doubling the rotation speed from the conventional 3,000 RPM to 6,000 RPM (FIG. 10). In addition, smooth rotation was achieved by converting the two-pole radially oriented ferrite magnet into a compression-molded rare earth ring magnet, which was then polar anisotropically magnetized to create a sinusoidal waveform in the distribution of the generated magnetic field. 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 bonded magnets, in other words, by replacing magnets with inferior performance, and the amount of magnetic energy used is reduced, if an eight-fold performance improvement 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 the fact that the magnetic poles of the ring magnet and the magnetic material are integrated and saturated with polar anisotropy, resulting in a strong bond between the ring magnet and the magnetic material of the rotor, which has the effect of generating a force that counteracts centrifugal force, and at the same time causes the magnetic field emitted from the ring magnet of the rotor to have a sinusoidal waveform (Fig. 5). [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 decided to improve the coaxiality of the magnetic field distribution by realizing pseudopolar anisotropic orientation. This will suppress the cogging torque of the motor and the generation of vibration. 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 designing is whether the ring magnet can withstand the large centrifugal force, and whether the adhesive strength between the ring magnet and the rotor body parts can withstand it. Even a slight misalignment in coaxiality or the rotational vibration of the motor creates stress concentration points at specific points on the joint surface between the magnet and the rotor, which causes cracks to form and lead to damage to the ring magnet. A common countermeasure is to install a non-magnetic shatterproof cover on the surface of the ring magnet and apply pressure from the outside to prevent damage from centrifugal force. However, this increases the gap between the magnet and the stator, making it impossible to achieve sufficient miniaturization.

[0019] In addition to the bonding force of the adhesive acting between the magnet and the magnetic material of the rotor body, the present invention strengthens the magnetic bonding force acting between the magnet and the magnetic material of the rotor body by pseudopolar anisotropic magnetization, thereby preventing the ring magnet from flying off due to centrifugal force. However, if a stress concentration point occurs at a specific location on the joint surface between the ring magnet and the rotor body, the ring magnet will be damaged.

[0020] Therefore, we discovered that the centrifugal force problem could be avoided by first making the ring magnet into divided arc-shaped magnets from the start to avoid the problem of stress concentration at specific points on the joint surface, and then by increasing the unevenness of the outer periphery of the rotor body and increasing the joint strength by utilizing a metal adhesive.

[0021] Furthermore, they discovered that by making the magnetic material between the arc-shaped magnets nonmagnetic and by magnetizing the magnetic poles with pseudopolar anisotropy, the magnetic flux flowing through the magnetic circuit increases, thereby increasing the motor torque. In other words, its greatest feature is that it enables high-speed rotation without installing a non-magnetic case on the surface of the ring magnet.

[0022] 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.

[0023] 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.

[0024] 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 is very small.

[0025] Furthermore, regarding the problem of rare earth bonded magnets having inferior magnetic strength compared to Nd sintered magnets, the magnetic material of the rotor body was changed to a stainless steel magnet, the ring magnet was divided into arc-shaped magnets and the space between the arc-shaped magnets was made non-magnetic, the gap with the stator was reduced to 0.5 mm or less, and the magnetic poles were magnetized pseudo-anisotropically. These and other devised magnetic circuit measures solved this problem, ultimately making it possible to reduce the size and weight of the entire motor by more than 50%.

[0026] In terms of rotor processing costs, previous methods using sintered Nd magnets were extremely expensive, requiring processing of the rotor body which contains the storage space for the Nd sintered magnets, as well as an assembly process for mounting and gluing the sintered magnets, and a process for adjusting the coaxiality.

[0027] The injection molding type of the present invention has a high yield rate of Nd bonded magnets, and the rotor body is made simply by processing it into an approximately cylindrical shape, and the rotor is completed simply by molding this together with the magnet in an integrated manner. This is an extremely simple process, and it is possible to significantly reduce manufacturing costs to about 1 / 5.

[0028] 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.

[0029] The SPM motor of the present invention comprises the above-mentioned rotor, and a stator having a coil disposed axially symmetrically on the outer periphery of the rotor and a yoke that constitutes a magnetic circuit on the outer periphery of the coil. The electromagnetic coil may optionally include teeth within the yoke coil or may have no teeth.

[0030] 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 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.

[0031] The manufacturing method for pseudo-polar anisotropic magnetization of magnetic poles is to manufacture an injection molding die for anisotropic magnetization. The injection molding conditions are die temperature and injection temperature 100-150°C, molding pressure 50-150°C, and injection pressure 50-150°C. 0MPa, injection speed: 50~150cm 3 / s. Here, the aligning magnetic field is set to 1T or more. Normally, a magnetic field of 3T 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 0.7T or less, and the magnetic powder can be saturate magnetized with a magnetic field strength of 1T, and the magnet can be oriented along the magnetic flux lines.

[0032] Moreover, since the magnetic powder is saturated and magnetized, the saturated 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 can be omitted. Effect of the Invention

[0033] 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]

[0034] [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] 1 is a cross-sectional view of a cylindrical (approximately cylindrical) laminate having protrusions made of a semi-hard magnetic material used in the present invention. [Diagram 5] 1 is a partially enlarged cross-sectional view of a cylindrical (approximately cylindrical) laminate having protrusions made of a semi-hard magnetic material used in the present invention. [Figure 6] This is a plan view showing the magnetic field and north and south poles of the arc-shaped pseudopolar anisotropic bonded magnet of the present invention. [Figure 7] Photographs comparing 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) a perspective view of a magnet as viewed from the axial direction of a neodymium sintered type rotor. [Figure 10] This is a cross-sectional view of a Nd sintered type rotor as seen from the side. [Figure 11] 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

[0035] Brushless SPM motors are In a brushless SPM motor consisting of a stator and a rotor, The rotor includes a rotor body, a ring magnet, and a rotating shaft, the rotor body is made of a substantially cylindrical composite magnetic material that circumscribes the rotating shaft, The substantially cylindrical composite material comprises a stainless steel magnet in a cylindrical body, and a non-magnetic portion consisting of an even number of protrusions (four or more) extending axially symmetrically from the cylindrical body, 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 arranged in an arc shape on the outer periphery of the stainless steel magnet between the protrusions of the non-magnetic portion, and is fixed to the outer periphery of the composite magnetic material, The magnet has an even number of magnetic poles, four or more, in which N poles and S poles are alternately arranged, and the magnetic poles are stainless steel magnets magnetized with pseudopolar anisotropy. 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.

[0036] In addition, the brushless SPM motor: In the rotor, The degree of unevenness of the outer periphery of the stainless steel magnet of the cylindrical body 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 stainless steel magnet.

[0037] In addition, the manufacturing method of the rotor of the 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.

[0038] A detailed explanation will be given below with reference to Figs. 1 to 7. <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 now be described.

[0039] <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.

[0040] <Rotor body> The rotor body 21 is made of a composite magnetic material and has a substantially cylindrical shape. Here, "approximately cylindrical" refers to a shape having a cylindrical main body with a hole in the center for attaching a rotating shaft, and in addition to the cylindrical main body, an even number of protrusions (four or more) extending axially symmetrically on the outer periphery (Figure 4). The composite magnetic material is made up of a stainless steel magnet (Cr-Ni stainless steel magnet) and a non-magnetic portion (Cr-Ni stainless steel). The rotor body 21 is composed of a stainless steel magnet and a non-magnetic portion 211 around its periphery, and the two are an integral alloy.

[0041] There is no particular restriction on the material of the stainless steel magnet 21, 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. The magnet is usually shaped as a laminate of thin plates with insulating coating on both sides.

[0042] Stainless steel magnets are made by changing the structure of Ni-based stainless steel from 100% austenite to one containing 80% or more martensite to create a semi-hard magnetic material, which is then magnetized to saturation to create 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.

[0043] The non-magnetic portion 211 is a portion where the magnetic permeability is 1.2 or less. Only the protruding portions of the semi-hard material of the stainless steel magnet that constitutes the rotor body 21 before it is magnetized to saturation are partially modified. The modification of the semi-hard magnetic material can be achieved by restoring the ferromagnetic martensite structure to a non-magnetic austenite structure. Such modification can be stably achieved by localized heating at 900°C or higher, or by irradiation with a laser or electron beam.

[0044] The manufacture of the rotor body will be explained with reference to FIG. 4 and its partial view, FIG. Thin plates of semi-hard magnetic material formed by cold working are punched into a roughly cylindrical shape (2A) and then laminated. A cylindrical main body 50 having a hole 52 for mounting a rotating shaft in the center is formed, and protrusions 51 are formed symmetrically on the outer periphery of the cylindrical main body 50. The outer periphery 51a of protrusions 51 forms a concentric circle with the outer periphery (broken line) of rare earth anisotropic bonded magnet 52m that is injected and filled, making it possible to keep the gap between the stator and rotor to 0.5 mm or less (2B).

[0045] <Rare earth anisotropic bonded magnet> It is preferable that the injection molded type rare earth anisotropic bonded magnet (magnetically anisotropic rare earth bonded magnet) has as high a maximum energy product as possible, and the present invention can be realized by adopting one having 10 MGOe to 25 MGOe. Although its magnetic performance is significantly inferior to that of sintered Nd magnets, which have a maximum energy product of 40 MGOe or more, the number of magnetic poles on the rotor's surface magnet is at least four, which are magnetized alternately as north and south poles, and are saturated with pseudopolar anisotropy via the magnetic material or stainless steel magnet (Figure 6).

[0046] 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. The injection-molded rare earth anisotropic bonded magnet is injected and filled into an arc consisting of an area 52m surrounded by the outer surface 50a of a rotor body 50 made of a semi-hard magnetic material as shown in Figure 5 and the side surfaces 51a and 51b of the adjacent modified non-magnetic protrusion portion 51.

[0047] Furthermore, the magnets 22 (22N, 22S) are magnetized with pseudopolar anisotropy, and therefore have a small demagnetizing field and can extract a relatively large magnetic flux. Furthermore, the space between the magnets has been changed to stainless steel magnets, making them non-magnetic, allowing the magnetic flux to flow more effectively toward the stator, resulting in an increase in the amount of magnetic flux (Figure 6). 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.

[0048] <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 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.

[0049] <Joint strength between magnet and rotor body> 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 surface of the rotor is covered with resin, which is then bonded to the resin of the injection molded magnet, thereby ensuring a great bonding strength.

[0050] 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 body, thereby increasing the joint surface area with the magnet.

[0051] Regarding the bonding strength of the surface magnet, whether or not it will break depends on the uniformity of the magnet's workmanship, the coaxiality of the rotor, the 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.

[0052] <Cost> The cost consists of the cost of manufacturing the magnetic material 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 rare earth bonded magnets on the outer periphery using an injection process. Because there are no costly parts with complex structures, there is no need for precision assembly processes, and the magnetization process can be omitted, and the amount of expensive rare earth elements used is small at less than 4g, it is believed that the rotors can be manufactured at production costs less than one-fifth the manufacturing costs of conventional products.

[0053] <Motor specifications> Output is 40W~400W, rotor speed is 120,000RPM~200,000RPM, 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

[0054] <First Example> This is an example of a 100W output motor. The rotor body of the brushless SPM motor uses an approximately cylindrical ring component made by punching out a thin plate of semi-hard magnetic material (stainless steel magnet base material) into an approximately cylindrical disk, which is then insulated on both sides and laminated.

[0055] The injection-molded anisotropic rare earth bonded magnet is formed in an arc shape on the outer periphery of the stainless steel magnet between the protrusions made of non-magnetic parts, 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: 100MPa, injection speed: 90cm 3 / sec.

[0056] The rotor's surface magnet has four magnetic poles, with the non-magnetic parts of the protrusions arranged axially symmetrically sandwiched between them, magnetized alternately to N and S poles, and saturated with pseudo-polar anisotropy. Furthermore, these magnets are molded using an 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.

[0057] 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.

[0058] 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.

[0059] The bonding strength of the surface magnets was evaluated using a rotational speed tester that could rotate at 200,000 rpm, and all ten rotors used in the experiment passed the test.

[0060] 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 bonded magnet on the outer periphery using an 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.

[0061] 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.

[0062] 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. [Industrial Applicability]

[0063] 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]

[0064] 1: Brushless SPM motor 2: Rotor 21: rotor body, 211: non-magnetic part, 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: rotating shaft 2A: Approximately disc-shaped punched material made of semi-hard magnetic material 50: rotor body base material, 50a: outer circumferential surface, 51: protrusion, 52: hole for rotating shaft 2B: Partial view of 2A 50: rotor body base material, 50a: outer circumferential surface, 51: protrusion, 51a: outer circumferential surface of protrusion, 51b: side surface of protrusion, 52m: filling region where rare earth anisotropic bonded magnet is injection molded 2C: Flux flow diagram of pseudopolar anisotropy 21: Rotor body (stainless steel magnet), 211: Protruding non-magnetic part, 22N: N pole of rare earth bonded magnet, 22S: S pole of rare earth bonded magnet 3: Stator 4: Rotation axis 6: Polar anisotropic magnetization pattern of the magnet in Patent Document 1 7: Rotor made of sintered Nd magnet 71: Case, 72: Sintered magnet, 72N: N pole of sintered magnet, 72S: S pole of sintered magnet, 73: Shaft

Claims

1. In a brushless SPM motor consisting of a stator and a rotor, The rotor includes a rotor body, a ring magnet, and a rotating shaft, the rotor body is made of a substantially cylindrical composite magnetic material that circumscribes the rotating shaft, The substantially cylindrical composite magnetic material comprises a stainless steel magnet in a cylindrical body, and a non-magnetic portion having an even number of protrusions (four or more) extending axially symmetrically from the cylindrical body; 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 arranged in an arc shape on the outer periphery of the stainless steel magnet between the protrusions made of the non-magnetic portion, and is fixed to the outer periphery of the composite magnetic material, The magnet has an even number of magnetic poles, four or more, in which N poles and S poles are alternately arranged, and the magnetic poles are stainless steel magnets magnetized with pseudopolar anisotropy. 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 stainless steel magnet of the cylindrical body 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 stainless steel magnet.

3. 3. The method for manufacturing a rotor for a brushless SPM motor according to claim 1, further comprising the steps of: 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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