Permanent magnet direct current motor

Abstract

The utility model discloses a permanent magnet direct current motor, which relates to the technical field of permanent magnet direct current motors and comprises a stator yoke, a permanent magnet is arranged in the stator yoke, a rotor iron core is further rotatably mounted in the stator yoke, a plurality of iron core grooves are arranged on the rotor iron core, and the number of the iron core grooves is eight. The eight iron core grooves are formed in the periphery of the rotor iron core at equal intervals, the number of the permanent magnets is two, the two permanent magnets are symmetrically installed on the inner side wall of the stator yoke, and the rotor iron core is located between the two permanent magnets; according to the permanent magnet direct current motor, skewed slots, skewed poles, rotor notch width reduction and inner and outer circle non-concentric magnets are not needed, only the pole-arc coefficient of the magnets needs to be selected to be 0.75-0.8, the permanent magnet direct current motor has the advantages of being small in cogging torque, electromagnetic vibration and electromagnetic noise and high in mechanical performance, especially when the pole-arc coefficient is 0.75, the cogging torque is close to 0, the cost performance is high, and the permanent magnet direct current motor is suitable for large-scale popularization and application. And the quality and economic benefits are obvious.

Description

Technical Field

[0001] This utility model relates to the field of permanent magnet DC motor technology, specifically a permanent magnet DC motor. Background Technology

[0002] A permanent magnet DC motor is a type of motor that uses permanent magnets to create a magnetic field. It is widely used in various portable electronic devices and appliances, such as tape recorders, VCD players, jukeboxes, electric massagers, and various toys. It is also increasingly used in the automotive, motorcycle, electric bicycle, battery-powered vehicle, shipbuilding, aviation, and machinery industries. Furthermore, it has wide applications in high-precision products such as video recorders, photocopiers, cameras, mobile phones, precision machine tools, banknote counting machines, medical instruments, and surgical tools. With the development of technology, the applications of permanent magnet DC motors will continue to expand. my country produces billions of permanent magnet DC motors annually. Permanent magnet DC motors possess excellent mechanical and regulatory characteristics, are small in size, highly efficient, have a wide speed range, a large starting torque, and are inexpensive.

[0003] However, in permanent magnet DC motors, the interaction between the permanent magnet and the slotted rotor core inevitably generates cogging torque, leading to torque fluctuations and causing vibration and noise. Cogging torque is the torque generated by the interaction between the permanent magnet and the rotor core when the permanent magnet motor windings are not energized. It is caused by fluctuations in the tangential component of the interaction force between the permanent magnet and the rotor teeth. When there is relative motion between the stator and rotor, the magnetic permeability between the rotor teeth and the permanent magnet in the pole arc region remains essentially unchanged, so the magnetic field around these rotor teeth also remains essentially unchanged. However, in a small region corresponding to the two sides of the permanent magnet, formed by one or two rotor teeth, the magnetic permeability changes significantly, causing changes in the stored energy of the magnetic field, thus generating cogging torque. Cogging torque is one of the unique problems of permanent magnet motors and a key issue that must be considered and solved in high-performance permanent magnet motors. The formula for cogging torque is as follows:

[0004]

[0005] Tcog(α, Ns): Cogging torque, La: Axial length of rotor core, μ0: Vacuum permeability, R1: Rotor core radius, R2: Stator yoke inner radius, Gn: Fourier decomposition coefficient of the square of relative air gap permeability, Br(nzNs / 2P): Fourier decomposition coefficient of the square of air gap magnetic flux density produced by the permanent magnet, α: Angle between the centerline of a specified rotor tooth and the centerline of a specified magnet, n: An integer that makes nz / 2p an integer, z: Number of rotor slots, Ns: Number of skewed slots of the rotor, θs1: Rotor tooth pitch in radians.

[0006] As can be seen from the above formula, methods to reduce cogging torque can be summarized into three main categories: methods of changing the permanent magnet pole parameters, methods of changing rotor parameters, and reasonable combinations of rotor slots and poles. Methods of changing magnetic pole parameters reduce cogging torque by altering the amplitude of Brn. These methods mainly include changing the pole arc coefficient, using magnets with non-concentric inner and outer circles, pole offset, skewed poles, and combinations of unequal pole arc coefficients. Methods of changing rotor parameters reduce cogging torque by altering the amplitude of Gn. These methods mainly include changing the slot width, changing the tooth shape, unequal slot width, and skewed slots. Reasonably selecting the number of rotor slots and magnet poles, and changing the frequency and magnitude of Brn and Gn, can also reduce cogging torque.

[0007] In motor design, appropriate methods to reduce cogging torque can be adopted based on actual conditions. These methods can be used individually or in combination. Commonly used methods include skewed slots, skewed poles, magnets with misaligned inner and outer diameters, and reducing rotor slot width. These methods are either positively or negatively correlated with cogging torque; that is, using them will have some effect. However, these methods generally increase costs or weaken the motor's mechanical performance. For example, skewed slots increase the difficulty of the winding process, limit the potential for increasing slot fill factor, and weaken the motor's mechanical performance; skewed poles increase the difficulty of the magnetization process; magnets with misaligned inner and outer diameters weaken the motor's performance; reducing the rotor slot width increases the difficulty of winding and prevents the use of thicker wire diameters. Optimizing the magnet's pole arc coefficient to reduce cogging torque is rarely used because cogging torque and the pole arc coefficient are not completely positively or negatively correlated. If the value is not within the appropriate range, cogging torque may increase, leading to a decrease in motor mechanical performance. However, finding the appropriate range for the magnet's pole arc coefficient using traditional methods is very complex and difficult.

[0008] The pole arc coefficient is equal to the ratio of the pole arc width to the pole pitch, expressed as αp=θ / (360 / 2P), where θ is the angle between the lines connecting the two ends of the magnet to the center of the circle, and P is the number of pole pairs of the motor. For example, P is 1 for a 2-pole motor, P is 2 for a 4-pole motor, and so on.

[0009] To address these issues, we designed a permanent magnet DC motor. Utility Model Content

[0010] The purpose of this invention is to provide a permanent magnet DC motor to solve the problems mentioned in the background art.

[0011] To solve the above-mentioned technical problems, this utility model provides a permanent magnet DC motor, including a stator yoke, in which a permanent magnet is disposed, and a rotor core is rotatably mounted in the stator yoke, wherein a plurality of core slots are formed on the rotor core.

[0012] Furthermore, the number of core slots is eight, and the eight core slots are equally spaced around the outside of the rotor core.

[0013] Furthermore, the number of permanent magnets is two, and the two permanent magnets are symmetrically installed on the inner sidewall of the stator yoke, with the rotor core located between the two permanent magnets.

[0014] Furthermore, one side of the stator yoke is integrally formed with a through hole, the permanent magnet is fixedly installed on the inner side wall of the through hole, and the rotor core is rotatably disposed in the through hole.

[0015] Furthermore, the polar arc coefficient of the rotor core is 0.75-0.8.

[0016] Furthermore, the stator yoke is made of low-carbon steel.

[0017] Furthermore, the rotor core is made of silicon steel sheets.

[0018] Compared with the prior art, the beneficial effects of this utility model are: the permanent magnet DC motor does not require skewed slots, skewed poles, reduced rotor slot width, or magnets with misaligned inner and outer circles. It only requires the pole arc coefficient of the magnet to be selected between 0.75 and 0.8. The permanent magnet DC motor is characterized by low cogging torque, low electromagnetic vibration and electromagnetic noise, and strong mechanical performance. In particular, when the pole arc coefficient is 0.75, the cogging torque is close to 0, resulting in high cost performance and significant quality and economic benefits. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the planar structure of the present invention;

[0020] Figure 2 The present invention uses Ansoft RMxprt parametric design to obtain the curves showing the relationship between different magnet pole arc coefficients and tooth cogging torque.

[0021] In the diagram: 1. Stator yoke; 2. Permanent magnet; 3. Rotor core; 4. Core slot. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0023] Please see Figure 1-2This utility model provides a technical solution: a permanent magnet DC motor, including a stator yoke 1, a permanent magnet 2 disposed inside the stator yoke 1, and a rotor core 3 rotatably mounted inside the stator yoke 1. The rotor core 3 has a plurality of core slots 4, the number of which is eight. The eight core slots 4 are equally spaced around the outside of the rotor core 3. The number of permanent magnets 2 is two, and the two permanent magnets 2 are symmetrically mounted on the inner sidewall of the stator yoke 1. The rotor core 3 is located between the two permanent magnets 2. The pole arc coefficient of the rotor core 3 is 0.75-0.8.

[0024] In practical implementation, Ansoft RMxprt was used for parametric design, with the pole arc coefficient ranging from 0.4 to 1 and a step size of 0.05. The relationship curve between cogging torque and pole arc coefficient was calculated. The curve shows that the pole arc coefficient is minimum at 0.5 and 0.75, and the motor's cogging torque is almost zero. Based on the positive correlation between motor mechanical performance and magnetic flux, and the positive correlation between magnetic flux and pole arc coefficient, the characteristics of the different schemes are as follows: Scheme 1: Pole arc coefficient between 0.4 and 0.48, maximum motor cogging torque, weakest mechanical performance; Scheme 2: Pole arc coefficient between 0.48 and 0.52, minimum motor cogging torque, relatively weak mechanical performance; Scheme 3: Pole arc coefficient between 0.52 and 0.72, relatively large motor cogging torque, moderate mechanical performance; Scheme 4: Pole arc coefficient between 0.72 and 0.8, minimum motor cogging torque, relatively strong mechanical performance; Scheme 5: Pole arc coefficient between 0.8 and 1.0, moderate motor cogging torque, strongest mechanical performance. Comparing the above solutions, the analysis shows that if a low cogging torque motor is required, solution 4 has the best cost performance, especially when the pole arc coefficient is 0.75 and the cogging torque is close to 0.

[0025] This permanent magnet DC motor eliminates the need for skewed slots, skewed poles, reduced rotor slot width, and magnets with misaligned inner and outer circles. It only requires selecting the pole arc coefficient of the magnet between 0.75 and 0.8. This permanent magnet DC motor is characterized by low cogging torque, low electromagnetic vibration and electromagnetic noise, and strong mechanical performance. In particular, when the pole arc coefficient is 0.75, the cogging torque is close to 0, resulting in high cost performance and significant quality and economic benefits.

[0026] See Figure 1-2 One side of the stator yoke 1 is integrally formed with a through hole, and the permanent magnet 2 is fixedly installed on the inner wall of the through hole. The rotor core 3 is rotatably installed in the through hole. This facilitates the proper installation of the permanent magnet 2 and the rotor core 3.

[0027] See Figure 1-2 The stator yoke 1 is made of low-carbon steel.

[0028] In practice, based on the above, low-carbon steel has good magnetic permeability and mechanical strength, which can meet the needs of motor operation.

[0029] See Figure 1-2 The rotor core 3 is made of silicon steel sheets.

[0030] In practical implementation, based on the above, silicon steel sheets have a high resistivity, which effectively reduces eddy current losses compared to other materials, such as carbon steel plates or pure iron. This low-loss characteristic helps reduce the energy consumption of the motor and improve its efficiency. In addition, silicon steel sheets can significantly improve magnetic aging phenomena, further reducing iron losses.

[0031] Working Principle: In use, Ansoft RMxprt is employed for parametric design, with the pole arc coefficient ranging from 0.4 to 1 and a step size of 0.05. The relationship curve between cogging torque and pole arc coefficient is calculated. The curve shows that the pole arc coefficient is minimized at 0.5 and 0.75, with the motor's cogging torque almost approaching zero. Based on the positive correlation between motor mechanical performance and magnetic flux, and the positive correlation between magnetic flux and pole arc coefficient, the characteristics of the following different schemes are as follows: Scheme 1: Pole arc coefficient between 0.4 and 0.48, maximum motor cogging torque, weakest mechanical performance; Scheme 2: Pole arc coefficient between 0.48 and 0.52, minimum motor cogging torque, relatively weak mechanical performance; Scheme 3: Pole arc coefficient between 0.52 and 0.72, relatively large motor cogging torque, moderate mechanical performance; Scheme 4: Pole arc coefficient between 0.72 and 0.8, minimum motor cogging torque, relatively strong mechanical performance; Scheme 5: Pole arc coefficient between 0.8 and 1.0, moderate motor cogging torque, strongest mechanical performance. Comparing the above solutions, the analysis shows that if a low cogging torque motor is required, solution 4 has the best cost performance, especially when the pole arc coefficient is 0.75 and the cogging torque is close to 0.

Claims

1. A permanent magnet DC motor, characterized in that, It includes a stator yoke (1), a permanent magnet (2) is provided inside the stator yoke (1), and a rotor core (3) is rotatably installed inside the stator yoke (1). The rotor core (3) has multiple core slots (4). The polar arc coefficient of the rotor core (3) is 0.75-0.

8. The stator yoke (1) is made of low carbon steel, and the rotor core (3) is made of silicon steel sheet.

2. A permanent magnet DC motor as described in claim 1, characterized in that: The number of the core slots (4) is eight, and the eight core slots (4) are equally spaced around the outside of the rotor core (3).

3. A permanent magnet DC motor as described in claim 1, characterized in that: The number of permanent magnets (2) is two, and the two permanent magnets (2) are symmetrically installed on the inner side wall of the stator yoke (1), and the rotor core (3) is located between the two permanent magnets (2).

4. A permanent magnet DC motor as described in claim 1, characterized in that: The stator yoke (1) has an integrally formed through hole on one side, the permanent magnet (2) is fixedly installed on the inner side wall of the through hole, and the rotor core (3) is rotatably installed in the through hole.

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