High-speed permanent magnet synchronous motor for dust collector

Abstract

The utility model relates to the technical field of motors, in particular to a high-speed permanent magnet synchronous motor for a dust collector. The motor comprises a motor shell, a stator iron core is arranged in the motor shell, a permanent magnet is concentrically arranged in the stator iron core, a rotor iron core is concentrically arranged in the permanent magnet, the stator iron core is of a three-groove structure, the permanent magnet is a bonded neodymium-iron-boron magnetic ring, the permanent magnet is subjected to dipolar magnetization, and the rotor iron core is of a three-groove structure. The ratio of the outer diameter of the permanent magnet to the outer diameter of the stator core is 0.2-0.4, and the difference between the radius of the inner circle diameter of the stator core and the radius of the outer circle of the permanent magnet is 0.2-0.5 mm. The device improves the efficiency of the motor, and solves the problems of serious heating of the rotor and high cost of sintered neodymium-iron-boron permanent magnets.

Description

Technical Field

[0001] The utility model relates to the technical field of motors, and particularly relates to a high-speed permanent magnet synchronous motor for a vacuum cleaner. Background Art

[0002] Existing household DC hand-held vacuum cleaners generally adopt permanent magnet synchronous motors with high rotational speeds. Compared with brushed motors, high-speed permanent magnet synchronous motors are smaller in volume, lighter in weight, longer in service life, and have higher rotational speeds and higher power densities. The rotational speeds of such motors generally exceed 90,000 rpm, that is, the mechanical rotation frequency exceeds 1,500 Hz. This motor usually adopts the space vector control method to generate sinusoidal current to drive the motor to operate, in order to reduce the motor vibration noise and improve the motor operation stability. Its circuit schematic diagram is as Figure 2 shown. When the space vector control method drives the motor, the switching frequency of the power switching tubes in the three-phase inverter bridge needs to be higher than a certain multiple of the motor rotational electrical frequency to obtain a sinusoidal current with less harmonics. Limited by the switching frequency of the power switching tubes, such motors usually adopt the minimum number of pole pairs design, that is, two-pole (one pair of poles) permanent magnets. This design scheme makes the motor rotational electrical frequency equal to the motor rotational mechanical frequency, reducing the requirement for the high switching frequency of the inverter bridge power switching tubes. The rotational electrical frequency of the motor is the motor mechanical rotation frequency multiplied by the number of pole pairs of the motor.

[0003] The disadvantages of the existing design scheme are as follows: 1. Sintered neodymium iron boron magnetic steel has a high conductivity, usually about 700,000 Siemens / meter. The rotational electrical frequency of such motors and the switching frequency of the power switching tubes are very high, and there is a high-frequency changing magnetic field in the air gap. Therefore, a large amount of eddy current loss will be induced in the sintered neodymium iron boron magnetic steel in such a high-frequency changing magnetic field. This loss not only reduces the motor performance and efficiency but also increases the risk of high-temperature demagnetization of the rotor; 2. Sintered neodymium iron boron magnetic steel has a high rare earth content, complex process, and high cost. 3. Sintered neodymium iron boron is easy to break, so it usually needs to be protected by a non-magnetic sheath. This sheath will occupy about 0.25 mm of the motor air gap. This leads to too large a motor air gap and reduces the power density of the motor. Summary of the Utility Model

[0004] In order to solve the problems described above, the utility model provides a high-efficiency high-speed permanent magnet synchronous motor for a vacuum cleaner, which solves the problems of high cost of the motor permanent magnet, serious rotor heating, and decline in motor performance.

[0005] To solve the above problems, the following technical solutions are provided:

[0006] A high-speed permanent magnet synchronous motor for a vacuum cleaner according to the present utility model includes a motor housing. A stator core is disposed inside the motor housing. The stator core has a three-slot structure. A permanent magnet is concentrically disposed inside the stator core. A rotor shaft is concentrically disposed inside the permanent magnet. The permanent magnet is an adhesive NdFeB magnetic ring. The number of magnetic poles of the permanent magnet for magnetization is two poles. The ratio of the outer diameter of the permanent magnet to the outer diameter of the stator core is between 0.2 and 0.4. The difference between the radius of the inner circle of the stator core and the outer radius of the permanent magnet is 0.2 mm to 0.5 mm.

[0007] In the above solution, the sintered NdFeB magnetic ring is replaced by an adhesive NdFeB magnetic ring. The permanent magnet is no longer a conductive material, and there is no high-frequency eddy current loss during operation, less heat is generated, and the temperature is low. Thus, the problem of overheating of the motor rotor is solved, the efficiency of the motor is improved, and the risk of demagnetization of the rotor permanent magnet due to overheating is reduced.

[0008] The stator core has a three-slot structure, with sufficient space for winding, reducing the winding current density and the copper loss of the motor winding.

[0009] The permanent magnet has two poles and is an adhesive NdFeB material with low remanence (the remanence is usually only about 0.65 Tesla), reducing the electrical frequency of the motor and the magnetic density in the iron core, thus greatly reducing the iron core loss of the motor.

[0010] In the above solution, by removing the rotor sheath and reducing the air gap of the motor, the energy efficiency of the motor is improved, and the energy conversion efficiency is higher, thus reducing energy waste and environmental pollution. The remanence of the adhesive NdFeB magnetic steel is about 0.65 Tesla, only about half of that of the sintered NdFeB magnetic steel. However, the tensile strength of the adhesive NdFeB magnetic steel made by applying high-strength glue materials and appropriate processes is much higher than that of the sintered NdFeB magnetic steel. Therefore, the rotor protective sleeve can be removed, which greatly reduces the actual air gap of the motor. In this design solution, the gap between the outer circle of the permanent magnet and the inner circle of the stator core is reduced from about 0.85 mm to 0.2 mm to 0.5 mm. This design solution uses the reduction of the air gap to make up for the loss of power density caused by the reduction of the remanence of the permanent magnet.

[0011] In the above solution, by setting the ratio of the outer diameter of the adhesive NdFeB magnetic ring to the outer diameter of the stator core to be between 0.2 and 0.4, the motor achieves the optimal cost performance. If the outer diameter of the magnetic ring is less than 0.2 times the outer diameter of the stator core, the amount of permanent magnet material used is too small, and the output power capacity of the motor is insufficient; if the outer diameter of the magnetic ring is greater than 0.4 times the outer diameter of the stator core, the thickness of the magnetic ring is too large, and a sheath is required to protect the magnetic ring, and the actual air gap of the motor cannot be reduced.

[0012] The stator core includes a stator yoke and three stator teeth. Each of the stator teeth is circumferentially and uniformly arranged along the inner wall surface of the stator yoke. Stator coils are provided on the stator teeth.

[0013] The permanent magnet is a two-pole non-conductive bonded neodymium iron boron cylindrical magnetic ring.

[0014] The stator core has a structure in which three stator teeth and three slots are alternately arranged.

[0015] The rated power of the motor is 100W to 1,500W.

[0016] The rated speed of the motor is 50,000 rpm / min to 350,000 rpm / min.

[0017] Adopting the above scheme, there are the following specific advantages:

[0018] 1. A high-speed permanent magnet synchronous motor for a vacuum cleaner according to the present utility model includes a motor housing. A stator core is arranged inside the motor housing. A permanent magnet is concentrically arranged inside the stator core. A rotor shaft is concentrically arranged inside the permanent magnet. The permanent magnet is a bonded neodymium iron boron magnetic ring. The bonded neodymium iron boron magnetic ring is a non-conductive material and has no eddy current loss in a high-frequency alternating magnetic field. Therefore, it generates less heat during operation, greatly improving the efficiency and reliability of the motor.

[0019] 2. This scheme adopts a two-pole three-slot structure. The motor has a lower electrical frequency during high-speed rotation, reducing the loss of the motor core. The three-slot structure enables the motor to have a larger winding area, reducing the current density of the motor winding and the copper loss of the motor winding.

[0020] 3. In this scheme, by selecting an appropriate ratio of the outer diameter of the magnetic ring to the outer diameter of the stator, and utilizing the high tensile stress of the bonded neodymium iron boron magnetic ring, the sheath on the surface of the magnetic ring is removed, reducing the actual air gap of the motor to 0.2mm to 0.5mm, greatly improving the power density of the motor, making up for the shortcoming of insufficient motor power caused by the low remanence of the bonded neodymium iron boron magnetic ring, and at the same time significantly reducing the cost. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the stator and rotor of a high-speed permanent magnet synchronous motor for a vacuum cleaner;

[0022] Figure 2 It is a schematic diagram of the control circuit of a high-speed permanent magnet synchronous motor for a vacuum cleaner;

[0023] Figure 3 It is a schematic diagram of the magnetic circuit of a sintered neodymium iron boron motor with an air gap of 0.85mm;

[0024] Figure 4 It is a schematic diagram of the magnetic circuit of a bonded neodymium iron boron motor with an air gap of 0.3mm;

[0025] Figure 5Schematic diagram of the working efficiency comparison between a sintered NdFeB motor with an air gap of 0.85 mm and an adhesive NdFeB motor with an air gap of 0.3 mm;

[0026] Figure 6 Schematic diagram of the comparison of stator iron loss, winding copper loss and permanent magnet eddy current loss between a sintered NdFeB motor with an air gap of 0.85 mm and an adhesive NdFeB motor with an air gap of 0.3 mm;

[0027] Description of the reference numerals: 1. Stator core; 101. Stator yoke; 102. Stator teeth; 2. Permanent magnet; 3. Rotor shaft; 4. Stator coil. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] As Figure 1 shown, a high-speed permanent magnet synchronous motor for a vacuum cleaner according to the present invention includes a motor housing. A stator core 1 is arranged inside the motor housing. A permanent magnet 2 is concentrically arranged inside the stator core 1. A rotor shaft 3 is concentrically arranged inside the permanent magnet 2. The permanent magnet 2 is an adhesive NdFeB magnetic ring. The adhesive NdFeB magnetic ring is a non-conductive material, has no eddy current loss, and has a low working temperature, greatly improving the performance and reliability of the motor.

[0030] The stator core 1 has a three-slot structure, which improves the winding area of the winding, reduces the current density of the winding, and reduces the copper loss of the winding. The permanent magnet 2 has two poles, which reduces the electrical frequency and makes the loss of the stator core smaller.

[0031] The ratio of the outer diameter of the permanent magnet 2 to the outer diameter of the stator core 1 is set between 0.2 and 0.4, which not only ensures sufficient magnetic field strength to obtain high power density of the motor, but also ensures that the outer diameter of the permanent magnet 2 is not too large, so that the tensile stress during high-speed operation is not too high. At the same time, since the bonded NdFeB material is used for the permanent magnet 2, its tensile strength is significantly higher than that of the sintered NdFeB. Therefore, the originally used sheath around the permanent magnet 2 is removed, so that the actual air gap of the motor is controlled between 0.2 mm and 0.5 mm. The smaller motor air gap greatly increases the power density of the motor, so that when the permanent magnet 2 uses the bonded NdFeB material with a remanence only about half of that of the sintered NdFeB, the motor can still obtain a considerable power density; because the bonded NdFeB has a small remanence and a small radial force wave of the motor air gap, the generation of noise can be reduced, and when the vacuum cleaner is working, the noise is significantly reduced, improving the user experience; the bonded NdFeB magnetic ring has less rare earth element content than the sintered NdFeB magnetic ring and a simple process, so the cost is reduced by nearly half.

[0032] The stator core 1 includes a stator yoke 101 and three stator teeth 102. Each of the stator teeth 102 is circumferentially and uniformly arranged along the inner wall surface of the stator yoke 101, and a stator coil 4 is arranged on the stator teeth 102.

[0033] In the background technology, the motor A with a sintered NdFeB as the permanent magnet 2 and a two-pole three-slot structure having an air gap of 0.85 mm is shown as Figure 3 shown; the motor B with a bonded NdFeB magnetic ring as the permanent magnet 2 and a two-pole three-slot structure having an air gap of 0.3 mm is shown as Figure 4 shown; by comparing the two, it can be obtained that the working efficiency of the motor B is higher than that of the motor A, as shown in Figure 5 shown; by comparing the two, it can be obtained that the loss of the stator core of the motor B is significantly lower than that of the stator core of the motor A, the copper loss of the winding of the motor B is slightly higher than that of the winding of the motor A, and the eddy current loss of the rotor of the motor B is significantly lower than the eddy current loss of the permanent magnet 2 of the motor A, as shown in Figure 6 shown. Therefore, the motor B using a bonded NdFeB magnetic ring with a small air gap as the permanent magnet 2 is superior to the motor A using a sintered NdFeB magnetic ring as the permanent magnet 2.

[0034] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model. In the description of the present utility model, unless otherwise specified and defined, it should be noted that the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two elements. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific situations.

[0035] The above are only the preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A high-speed permanent magnet synchronous motor for a vacuum cleaner, characterized in that: The invention comprises a motor housing, wherein a stator core (1) is arranged in the motor housing, wherein the stator core (1) has a three-slot structure, wherein a permanent magnet (2) is concentrically arranged inside the stator core (1), wherein a rotor shaft (3) is concentrically arranged inside the permanent magnet (2), wherein the permanent magnet (2) is a bonded neodymium iron boron magnetic ring, wherein the number of magnetized poles of the permanent magnet (2) is two, wherein the ratio of the outer diameter of the permanent magnet (2) to the outer diameter of the stator core (1) is between 0.2 and 0.4, and the difference between the inner radius of the stator core (1) and the outer radius of the permanent magnet (2) is between 0.2 mm and 0.5 mm.

2. A high-speed permanent magnet synchronous motor for a vacuum cleaner as claimed in claim 1, characterized in that: The permanent magnet (2) is a two-pole non-conductive bonded NdFeB cylindrical magnetic ring.

3. A high-speed permanent magnet synchronous motor for a vacuum cleaner as claimed in claim 1, characterized in that: The stator core has a structure in which three stator teeth (102) and three slots are alternately arranged.

4. A high-speed permanent magnet synchronous motor for a vacuum cleaner as claimed in claim 1, characterized in that: The stator core (1) comprises a stator yoke (101) and three stator teeth (102), each of the stator teeth (102) being evenly arranged in the circumferential direction along the inner wall surface of the stator yoke (101), and a stator coil (4) being arranged on the stator teeth (102).

5. A high-speed permanent magnet synchronous motor for a vacuum cleaner as claimed in claim 1, characterized in that: Motor power ratings range from 100W to 1,500W.

6. A high-speed permanent magnet synchronous motor for a vacuum cleaner as claimed in claim 1, characterized in that: The rated motor speed is 50,000rpm / min to 350,000rpm / min.

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