High-speed permanent magnet brushless motor for dust collector

Abstract

The utility model relates to the technical field of motors, in particular to a high-speed permanent magnet brushless motor for a dust collector. The permanent magnet 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 permanent magnet is a bonded neodymium iron boron magnetic ring, the permanent magnet is subjected to quadrupole magnetization, and the ratio of the outer diameter of the magnetic ring to the outer diameter of the stator iron core is 0.2-0.45. And a rotor sheath is arranged at the periphery of the permanent magnet. The device solves the problems of serious heating of the motor rotor, reduction of motor performance and high cost of the permanent magnet.

Description

Technical Field

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

[0002] Current household DC handheld vacuum cleaners generally use high-speed permanent magnet brushless motors. Compared to brushed motors, high-speed permanent magnet brushless motors have the advantages of long life, high speed, high power density, small size, and light weight. The speed of such high-speed brushless motors can even exceed 150,000 rpm, which means the mechanical rotation frequency exceeds 2,500 Hz. To reduce motor vibration and noise and improve motor operation stability, such motors usually use space vector control to generate a sinusoidal current to drive the motor. The circuit diagram is shown below. Figure 2 When the space vector control method is used to drive the motor, the switching frequency of the power switch tubes in the three-phase inverter bridge needs to be higher than a certain multiple of the motor's rotational frequency in order to obtain a sinusoidal current with fewer harmonics. Due to the switching frequency limitations of the power switch tubes in the past, such high-speed brushless motors usually adopt a design with a minimum number of pole pairs, that is, two poles and three slots, such as Figure 3 This design ensures that the motor's electrical frequency equals its mechanical frequency, reducing the need for high switching frequencies in the inverter bridge power switches. The motor's electrical frequency is the motor's mechanical frequency multiplied by the number of motor pole pairs.

[0003] Existing high-speed permanent magnet brushless motors of this type, which use a two-pole, three-slot design, typically use sintered NdFeB rings with high remanence to achieve high power density. The remanence of these sintered NdFeB rings is approximately 1.2 Tesla. These rings are typically designed as cylinders and fastened directly to the rotor shaft. They are protected by a non-magnetic protective sheath to prevent the permanent magnets from breaking under tensile stress during high-speed rotation. The disadvantages of existing designs are: 1. Sintered NdFeB magnets have a high electrical conductivity, typically around 700,000 Siemens / meter. The rotational frequency and switching frequency of these motors' power switches are both very high, resulting in a high-frequency magnetic field in the air gap. Therefore, sintered NdFeB magnets will induce a large amount of eddy current loss in such a high-frequency changing magnetic field. This loss not only reduces the performance and efficiency of the motor but also increases the risk of high-temperature demagnetization of the rotor, causing the motor performance to decline; 2. Sintered NdFeB magnets have a high rare earth content, complex process and high cost. Utility Model Content

[0004] In order to solve the problems in the related art, the utility model provides a high-speed permanent magnet brushless motor for a vacuum cleaner, which solves the problems of severe heating of the motor rotor and degradation of the motor performance.

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

[0006] The utility model discloses a high-speed permanent magnet brushless motor for a vacuum cleaner, comprising a motor housing, a stator core disposed in the motor housing, a permanent magnet concentrically disposed inside the stator core, a rotor shaft concentrically disposed inside the permanent magnet, the permanent magnet being a bonded neodymium iron boron magnetic ring, the permanent magnet being a quadrupole, and the ratio of the outer diameter of the magnetic ring to the outer diameter of the stator core being between 0.2 and 0.45.

[0007] In the above scheme, the original sintered NdFeB magnetic ring is replaced by the setting of bonding 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, thereby solving the problem of motor rotor overheating, improving the efficiency of the motor, and reducing the risk of overheating and demagnetization of the rotor permanent magnet. By setting the ratio of the outer diameter of the bonded NdFeB magnetic ring to the outer diameter of the stator core to be between 0.2 and 0.45, the motor achieves the best cost performance. If the outer diameter of the magnetic ring is less than 0.2 times the outer diameter of the stator core, the output capacity of the motor is insufficient; if the outer diameter of the magnetic ring is greater than 0.45 times the outer diameter of the stator core, the thickness of the magnetic ring is too large and the cost is too high. The ratio is between 0.2 and 0.45, which reduces the cost of the permanent magnet.

[0008] The rated speed of the motor is 50,000 rpm / min to 350,000 rpm / min, and the rated power of the motor is 100W to 1,500W.

[0009] The permanent magnet is a four-pole non-conductive bonded NdFeB magnetic ring, and the stator core is a six-slot, three-slot or single-phase motor four-slot structure.

[0010] The above scheme improves the energy efficiency of the motor through the four-pole setting, and the energy conversion efficiency is higher, thereby reducing energy waste and environmental pollution. The remanence of the bonded NdFeB magnet is about 0.65 Tesla, which is only about half of the remanence of the sintered NdFeB magnet. In order to make the motor using the bonded NdFeB magnet ring have the same power density as the motor using the original sintered NdFeB magnet ring, this design scheme changes the rotor permanent magnet from two poles to four poles. This design scheme uses the increase in the motor's electrical frequency to compensate for the loss of power density caused by the reduction in the remanence of the permanent magnet. In addition, due to the significant reduction in air gap flux density, the stator core loss of the motor using the four-pole bonded NdFeB magnet ring design scheme is lower than that of the original motor, and there is no significant increase in stator core loss due to doubling the electrical frequency.

[0011] A rotor sheath is provided around the permanent magnet, and the rotor sheath is made of a non-magnetic and non-conductive material, such as carbon fiber or glass fiber.

[0012] The stator core includes a stator yoke and a plurality of stator teeth, and stator coils are arranged on the stator teeth.

[0013] The above solution has the following advantages:

[0014] 1. The utility model relates to a high-speed permanent magnet brushless motor for a vacuum cleaner, comprising a motor housing, a stator core disposed in the motor housing, a permanent magnet concentrically disposed inside the stator core, a rotor shaft concentrically disposed inside the permanent magnet, the permanent magnet being a bonded NdFeB magnetic ring, a four-pole permanent magnet, the ratio of the outer diameter of the magnetic ring to the outer diameter of the stator core being between 0.2 and 0.45, and the setting of the bonded NdFeB magnetic ring replacing the original sintered NdFeB magnetic ring, the permanent magnet is no longer a conductive material, and there is no high-frequency eddy current loss during operation, and heat is generated during operation. Less, low temperature, improves the efficiency and reliability of the motor, reduces the risk of overheating and demagnetization of the rotor permanent magnet, and sets the ratio of the outer diameter of the bonding NdFeB magnetic ring to the outer diameter of the stator core between 0.2 and 0.45, so that the motor achieves the best cost performance. If the outer diameter of the magnetic ring is less than 0.2 times the outer diameter of the stator core, the output capacity of the motor is insufficient. If the outer diameter of the magnetic ring is greater than 0.45 times the outer diameter of the stator core, the thickness of the magnetic ring is too large and the cost is too high. The ratio is between 0.2 and 0.45 to reduce the cost of the permanent magnet.

[0015] 2. The permanent magnets are four-pole, non-conductive, bonded NdFeB rings, improving motor efficiency and energy conversion efficiency, thereby reducing energy waste and environmental pollution. Replacing the original two-pole sintered NdFeB rings with four-pole bonded NdFeB rings reduces remanence while maintaining virtually unchanged power density, reducing noise and significantly lowering costs, resulting in greater energy conservation and environmental protection. A rotor shield is placed between the permanent magnets and the stator core to protect the rotor from centrifugal forces at high speeds. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of the stator and rotor of a high-speed permanent magnet brushless motor for a vacuum cleaner;

[0017] Figure 2 This is a schematic diagram of a high-speed permanent magnet brushless motor control circuit for a vacuum cleaner;

[0018] Figure 3 A schematic diagram of the magnetic field distribution of a high-speed permanent magnet brushless motor with a two-pole and three-slot structure for vacuum cleaners;

[0019] Figure 4 A schematic diagram of the magnetic field distribution of a high-speed permanent magnet brushless motor with a four-pole and six-slot structure for vacuum cleaners;

[0020] Figure 5 This is a schematic diagram comparing the working efficiency of a four-pole six-slot bonded NdFeB motor and a two-pole three-slot sintered NdFeB motor;

[0021] Figure 6A schematic diagram comparing the stator iron loss, winding copper loss, and permanent magnet eddy current loss of a four-pole, six-slot bonded NdFeB motor and a two-pole, three-slot sintered NdFeB motor.

[0022] Figure 7 A schematic diagram comparing the radial stress in the air gap between a four-pole, six-slot bonded NdFeB motor and a two-pole, three-slot sintered NdFeB motor.

[0023] Explanation of the accompanying drawings: 1. stator core; 101. stator yoke; 102. stator teeth; 2. permanent magnet; 3. rotor shaft; 4. rotor sheath; 5. stator coil. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] like Figure 1 As shown, the utility model is a high-speed permanent magnet brushless motor for a vacuum cleaner, including a motor housing, a stator core 1 is arranged in 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 a bonded NdFeB magnetic ring, and the number of magnetized poles of the permanent magnet 2 is four poles. The bonded NdFeB magnetic ring is a non-conductive material, has no eddy current loss, and has a low operating temperature, which greatly improves the performance and reliability of the motor.

[0026] The rated speed of the motor is 50,000 rpm / min to 350,000 rpm / min, and the rated power of the motor is 100W to 1,500W.

[0027] The permanent magnet 2 is a quadrupole, which improves the energy efficiency of the motor and has a higher energy conversion efficiency. It ensures that the motor has the same power density while the residual magnetism of the bonded NdFeB is only about half of that of the sintered NdFeB, reduces the motor noise and reduces the motor cost.

[0028] A rotor sheath 4 is provided around the permanent magnet 2 to protect the rotor from being damaged by centrifugal force at high speed. The rotor sheath 4 is preferably non-magnetic and non-conductive to avoid magnetic leakage and eddy current loss.

[0029] The stator core 1 includes a stator yoke 101 and stator teeth 102 , and the stator coils 5 are provided on the stator teeth 102 .

[0030] When the permanent magnet 2 is a bonded NdFeB magnetic ring, the magnetic properties of the bonded NdFeB magnetic ring are not high. Due to technological innovation, the performance of the MOS tube has been improved, and the operating frequency of the vacuum cleaner inverter has reached the requirements of the four-pole motor (this point is a prior art and will not be repeated here), that is, a four-pole motor can be used as the power source of the vacuum cleaner. The bonded NdFeB magnetic ring is a non-conductive material, has no high-frequency eddy current loss, and generates little heat, which greatly improves the reliability of the motor. Since the bonded NdFeB magnetic ring has a small residual magnetism and a small radial force wave in the motor air gap, it can reduce the generation of noise. When the vacuum cleaner is working, the noise is significantly reduced, which improves the user experience. The bonded NdFeB magnetic ring has less rare earth element content than the sintered NdFeB magnetic ring, and the process is simpler, so the cost is reduced by nearly half.

[0031] In the background technology, a two-pole three-slot motor using sintered aluminum iron boron as a permanent magnet 2 is a motor A. Figure 3 As shown, a four-pole six-slot motor using bonded NdFeB magnetic rings as permanent magnets 2 is motor B. Figure 4 As shown in the figure, by comparing the two, it can be seen that the working efficiency of motor B is higher than that of motor A. Figure 5 As shown, by comparing the two, it can be seen that the loss of the stator core 1 of motor B is lower than the loss of the stator core 1 of motor A, and the eddy current loss of the permanent magnet 2 of motor B is significantly lower than the eddy current loss of the permanent magnet 2 of motor B, as shown in Figure 6 Comparing the two, it can be seen that the radial air gap stress of motor B is significantly smaller than that of motor A. Therefore, motor A using a four-pole bonded NdFeB magnetic ring as permanent magnet 2 is superior to motor B using a two-pole sintered NdFeB magnetic ring as permanent magnet.

[0032] In the description of the present invention, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply 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 understood as a limitation on the present invention. In the description of the present invention, unless otherwise specified and limited, 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 internal communication of two elements, it can be a direct connection, or it can be an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0033] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-speed permanent magnet brushless 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, 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 a bonded neodymium iron boron magnetic ring, the number of magnetized poles of the permanent magnet (2) is four, and 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.

45.

2. A high-speed permanent magnet brushless motor for a vacuum cleaner according to claim 1, characterized in that: The rated speed of the motor is 50,000 rpm / min to 350,000 rpm / min, and the rated power of the motor is 100W to 1,500W.

3. The high-speed permanent magnet brushless motor for a vacuum cleaner according to claim 1, characterized in that: The permanent magnet (2) is a four-pole non-conductive bonded neodymium iron boron magnetic ring, and the stator core (1) is a six-slot, three-slot or four-slot structure of a single-phase motor.

4. A high-speed permanent magnet brushless motor for a vacuum cleaner according to claim 1, characterized in that: A rotor sheath (4) is provided on the periphery of the permanent magnet (2), and the rotor sheath (4) is made of a non-magnetic and non-conductive material, such as carbon fiber or glass fiber.

5. The high-speed permanent magnet brushless motor for a vacuum cleaner according to claim 1, characterized in that: The stator core (1) comprises a stator yoke (101) and a plurality of stator teeth (102), and stator coils (5) are provided on the stator teeth (102).

Images