Single-phase brushless DC motors and electrical equipment

Abstract

The present invention provides a single-phase brushless DC motor and electrical equipment. The single-phase brushless DC motor includes a stator and a rotor. The stator includes a stator core, which includes a stator yoke and an even number of stator teeth connected to the stator yoke. Each stator tooth includes a tooth body extending radially and a tooth crown connected to the end of the tooth body. The tooth crown includes two pole shoes, which extend toward either side of the corresponding tooth body along the direction of rotation of the rotor. The number of poles of the rotor is three times the number of stator teeth. Through the above design, the number of pole pairs of the stator and rotor is unequal. After modulation, the rotor magnetic field interacts with the stator magnetic field to generate more operating harmonics, thereby achieving the torque amplification effect of the vernier permanent magnet motor, increasing the motor's output torque and improving the motor's operating efficiency. At the same time, the harmonic content in the motor's back electromotive force is lower, the waveform is more sinusoidal, the motor runs more smoothly, and the torque fluctuation is smaller, which is conducive to improving the motor's vibration and noise performance.

Description

Technical Field

[0001] The present invention relates to the technical field of motors, and in particular to a single-phase brushless DC motor and an electrical device comprising the single-phase brushless DC motor. Background Art

[0002] Single-phase brushless DC motors (BLDCs) are characterized by their small size, light weight, simple structure, and low manufacturing cost. They are often used in low-power devices such as water pumps, refrigerator fans, and computer drive motors. However, existing single-phase BLDC motors have a four-slot, four-pole structure, which presents challenges such as low output torque, low efficiency, and high torque ripple. Summary of the Invention

[0003] In order to solve at least one of the above technical problems, an object of the present invention is to provide a single-phase brushless DC motor.

[0004] Another object of the present invention is to provide an electrical device comprising the above-mentioned single-phase brushless DC motor.

[0005] To achieve the above-mentioned objectives, the technical solution of the first aspect of the present invention provides a single-phase brushless DC motor, comprising: a stator, wherein the stator comprises a stator core and a winding wound around the stator core, the stator core comprises a stator yoke and an even number of stator teeth connected to the stator yoke, wherein any stator tooth comprises a tooth body extending in the radial direction and a tooth crown connected to the end of the tooth body, the tooth crown comprises two pole shoes, and the two pole shoes extend toward both sides of the corresponding tooth body along the rotation direction of the rotor; and a rotor, wherein the rotor cooperates with the stator and is suitable for rotating relative to the stator, and the number of poles of the rotor is three times the number of the stator teeth.

[0006] The single-phase brushless DC motor provided by the technical solution of the first aspect of the present invention has a stator with N poles (N is an even number) and a rotor with 3N poles. The 2N pole shoes of the stator serve to modulate the magnetic field. Through the above design, the number of pole pairs of the stator and rotor is unequal. After modulation, the rotor magnetic field can interact with the stator magnetic field to produce more operating harmonics, thereby achieving the effect of torque amplification of the vernier permanent magnet motor, increasing the output torque of the motor, and improving the motor's operating efficiency. At the same time, the above design makes the harmonic content in the motor's back electromotive force lower, the waveform more sinusoidal, the motor operation more stable, and the torque fluctuation is also smaller, which is conducive to improving the vibration and noise performance of the motor.

[0007] Specifically, in this application, the stator pole shoes serve as modulation units, modulating the magnetic field. The number of stator teeth is N, and each tooth has two pole shoes on the left and right. Therefore, the number of pole shoes is 2N, meaning the number of modulation units is 2N. Since the motor is a single-phase motor, the number of stator pole pairs is N / 2, while the number of rotor pole pairs is 3N / 2. The stator and rotor pole pairs are not equal. However, the sum of the stator and rotor pole pairs equals the number of modulation units. Therefore, after passing through the modulation units, the rotor magnetic field interacts with the stator magnetic field to generate torque, achieving a magnetic field modulation torque amplification effect. After modulation, the motor's no-load back EMF fundamental wave content is higher, which helps increase the motor's output torque and improve its operating efficiency. Furthermore, the back EMF after modulation has lower harmonic content and a more sinusoidal waveform, resulting in smoother motor operation and less torque fluctuation, which helps improve the motor's vibration and noise performance.

[0008] In addition, the single-phase brushless DC motor in the above technical solution provided by the present invention may also have the following additional technical features:

[0009] In the above technical solution, a groove is provided at a position of the tooth crown facing the end surface of the rotor and opposite to the tooth body, and the groove is located between the two pole shoes.

[0010] Providing a groove on the air gap side of the tooth crown can increase the magnetic resistance of the leakage magnetic circuit, reduce the inter-pole leakage magnetic flux, thereby increasing the output power of the motor and improving the utilization rate of the permanent magnet.

[0011] In the above technical solution, the cross section of the groove is symmetrically arranged relative to the center line of the cross section of the tooth body; or the cross section of the groove is asymmetrically arranged relative to the center line of the cross section of the tooth body.

[0012] The cross section of the groove is symmetrically arranged relative to the center line of the cross section of the tooth body, so that the structure of the stator core is more regular and easy to process and shape.

[0013] The groove's cross-section is asymmetrical relative to the centerline of the tooth body, creating a certain offset angle between the stator and rotor magnetic fields. This creates a specific starting angle during motor startup, avoiding dead spots and enabling self-starting, thus resolving the dead-spot issue with single-phase motors. Furthermore, the groove's asymmetric structure allows the rotor to have varying bidirectional starting capabilities, making it particularly suitable for applications requiring different bidirectional starting capabilities, such as power tools and window lifts.

[0014] It can be understood that, in the present application, the center line of the cross section of the tooth body refers to a straight line that intersects the central axis of the stator yoke at right angles, extends in the radial direction of the stator yoke, and bisects the cross section of the tooth body.

[0015] In the above technical solution, the two ends of the cross section of the groove along the rotation direction of the rotor are respectively recorded as the first end and the second end, and the distance between the first end and the center line of the cross section of the tooth body is greater than or less than the distance between the second end and the center line of the cross section of the tooth body.

[0016] This design can make the center line of the stator magnetic field and the center line of the rotor magnetic field not coincide with each other, thereby generating a certain starting angle when the motor starts, thereby avoiding the dead point position and achieving starting.

[0017] In the above technical solution, the cross section of the groove is U-shaped, V-shaped or arc-shaped.

[0018] The cross section of the groove is U-shaped, with a simple structure and easy processing and forming.

[0019] The cross section of the groove is V-shaped or arc-shaped, which is convenient for forming a non-uniform air gap between the stator and the rotor, is beneficial for avoiding the dead point position, and is convenient for starting the motor. The structure is simple and easy to process and form.

[0020] In the above technical solution, the width of the groove along the rotation direction of the rotor is greater than the width of the tooth body along the rotation direction of the rotor.

[0021] This design, on the one hand, is conducive to further increasing the magnetic resistance of the leakage magnetic circuit, further reducing the inter-pole leakage magnetic field, thereby further improving the output power of the motor and further improving the utilization rate of the permanent magnet; on the other hand, by controlling the position of the circumferential ends of the groove, it is convenient for the two pole shoes on both sides of the same tooth body to form an asymmetric structure, and then form an asymmetric air gap structure between the stator and the rotor, which will make the centers of the stator magnetic field and the rotor magnetic field not coincide, thereby realizing motor starting.

[0022] Of course, the width of the groove along the rotation direction of the rotor may also be equal to or smaller than the width of the tooth body along the rotation direction of the rotor.

[0023] In any of the above technical solutions, the distance between the pole shoe and the rotor varies along the circumference of the rotor, so that a non-uniform air gap is formed between the stator and the rotor.

[0024] By controlling the spacing between the pole shoes and the rotor, a non-uniform air gap is created between the stator and rotor, helping to avoid dead spots and facilitate motor starting. Furthermore, the unequal air gaps between each pole shoe and the rotor reduce the motor's effective air gap, enabling startup while maintaining high output performance.

[0025] In any of the above technical solutions, the two pole shoes of the same stator tooth are respectively recorded as the first pole shoe and the second pole shoe, and the first pole shoe and the second pole shoe form an asymmetric structure with respect to the median vertical plane of the tooth body of the same stator tooth, and the median vertical plane passes through the central axis of the stator yoke.

[0026] The asymmetric design of the first pole shoe and the second pole shoe can generate a certain offset angle between the stator magnetic field and the rotor magnetic field, thereby realizing self-starting of the single-phase motor and solving the starting dead point problem of the single-phase motor.

[0027] It is understood that in this application, the mid-vertical plane of the tooth body refers to the plane passing through the central axis of the stator yoke and bisecting the tooth body vertically. The projection of the mid-vertical plane on the cross section of the tooth body is the center line of the cross section of the tooth body.

[0028] Of course, the first pole shoe and the second pole shoe of the same stator tooth can also be arranged symmetrically about the median vertical plane of the corresponding tooth body. This is conducive to simplifying the structure of the stator core, facilitating processing and forming, and forming symmetrical and equal-thickness air gaps, which is conducive to reducing motor vibration and noise, making the motor run more smoothly, and enhancing the smoothness of motor startup.

[0029] In the above technical solution, the length of the surface of the first pole shoe facing the rotor along the rotation direction of the rotor is less than or greater than the length of the surface of the second pole shoe facing the rotor along the rotation direction of the rotor; and / or the area of ​​the surface of the first pole shoe facing the rotor is less than or greater than the area of ​​the surface of the second pole shoe facing the rotor.

[0030] The surface of the pole shoe facing the rotor is called the working surface of the pole shoe (or the pole face of the pole shoe). The circumferential lengths of the working surfaces of the first and second pole shoes on the same stator tooth are unequal, forming an asymmetric design and an asymmetric air gap structure between the stator and rotor. This prevents the centers of the stator and rotor magnetic fields from coinciding, creating a certain offset angle between the stator and rotor magnetic fields, thereby enabling self-starting of the motor.

[0031] Similarly, the working surfaces of the first and second pole shoes on the same stator tooth have unequal areas, creating an asymmetric design and an asymmetric air gap between the stator and rotor. This prevents the centers of the stator and rotor magnetic fields from aligning, creating a certain offset angle between them and enabling the motor to self-start.

[0032] In the above technical solution, the distance between the surface of the first pole shoe facing the rotor and the central axis of the stator yoke is recorded as the first distance, and the distance between the surface of the second pole shoe facing the rotor and the central axis of the stator yoke is recorded as the second distance; at least one of the first distance and the second distance gradually decreases or gradually increases along the rotation direction of the rotor; and / or at least one of the radial thickness of the first pole shoe and the radial thickness of the second pole shoe gradually decreases in the direction away from the corresponding tooth body.

[0033] The distance between the working surface of the pole shoe and the central axis of the stator yoke gradually increases or decreases, creating a non-uniform air gap between the pole shoe and the rotor's permanent magnets. This helps avoid dead spots and facilitates motor startup. Furthermore, the rotor's permanent magnets can adopt a regular, uniform thickness structure, simplifying the rotor structure. This also facilitates the formation of unequal air gaps between each pole shoe and the rotor, reducing the motor's equivalent air gap and enabling startup while maintaining high output performance.

[0034] The radial thickness of the pole shoe gradually decreases in the direction away from the corresponding tooth body (i.e., the tooth body connected to the pole shoe), so that the magnetic resistance of the pole shoe gradually increases in the direction away from the corresponding tooth body. Such a design can improve the air gap magnetic field waveform, making the waveform smoother, thereby making the motor run more smoothly and start more reliably.

[0035] In any of the above technical solutions, the rotor includes a rotor yoke and a permanent magnet; the radial thickness of the permanent magnet gradually decreases or increases along the rotation direction of the rotor.

[0036] The radial thickness of the permanent magnets gradually decreases or increases along the direction of rotor rotation, creating a non-uniform air gap between the pole shoes and the rotor's permanent magnets. This helps avoid dead spots and facilitates motor startup. Furthermore, the working surface of the pole shoes can be a circular arc concentric with the stator yoke, simplifying the stator structure. This also allows for unequal air gaps to be formed between each pole shoe and the rotor, reducing the motor's effective air gap and enabling startup while maintaining high output performance.

[0037] In any of the above technical solutions, the rotor is sleeved on the inner side of the stator; or the rotor is sleeved on the outer side of the stator.

[0038] The rotor is sleeved on the inner side of the stator to form an inner rotor motor. The rotor is sleeved on the outer side of the stator to form an outer rotor motor.

[0039] The technical solution of the second aspect of the present invention provides an electrical device, comprising: a device body; and a single-phase brushless DC motor as described in any one of the technical solutions of the first aspect, connected to the device body.

[0040] The electrical device provided by the technical solution of the second aspect of the present invention includes the single-phase brushless DC motor described in any one of the technical solutions of the first aspect, and thus has all the beneficial effects of any of the above technical solutions, which will not be repeated here.

[0041] In the above technical solution, the electrical equipment may be, but is not limited to, low-power equipment such as a water pump, a refrigerator fan, and a computer.

[0042] Additional aspects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0044] Figure 1 is a schematic diagram of a single-phase brushless DC motor according to an embodiment of the present invention;

[0045] Figure 2 yes Figure 1 The no-load magnetic field line distribution diagram of the single-phase brushless DC motor shown;

[0046] Figure 3 1. A comparison diagram of the no-load back EMF waveforms of the single-phase brushless DC motor of the present invention and the single-phase brushless DC motor of the prior art;

[0047] Figure 4 1. A comparison diagram of the Fourier decomposition results of the no-load back electromotive force of the single-phase brushless DC motor of the present invention and the single-phase brushless DC motor of the prior art;

[0048] Figure 5 is a schematic diagram of a single-phase brushless DC motor according to an embodiment of the present invention;

[0049] Figure 6 is a schematic diagram of a single-phase brushless DC motor according to an embodiment of the present invention;

[0050] Figure 7 is a schematic block diagram of an electrical device according to some embodiments of the present invention.

[0051] in, Figures 1 to 7 The corresponding relationship between the reference numerals and component names is as follows:

[0052] 1 stator, 11 stator core, 111 stator yoke, 112 tooth body, 113 tooth crown, 1131 groove, 1132 first pole shoe, 1133 second pole shoe, 12 winding;

[0053] 2 rotor, 21 rotor yoke, 22 permanent magnet;

[0054] 100 electrical equipment, 102 equipment body, 104 single-phase brushless DC motor. DETAILED DESCRIPTION

[0055] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0056] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0057] Refer to the following Figures 1 to 7 The single-phase brushless DC motor and electrical equipment according to some embodiments of the present invention are described.

[0058] like Figure 1 、 Figure 5 and Figure 6 As shown, the single-phase brushless DC motor 104 provided by the embodiment of the first aspect of the present invention includes: a stator 1 and a rotor 2.

[0059] Specifically, the stator 1 includes a stator core 11 and a winding 12 wound around the stator core 11. The stator core 11 includes a stator yoke 111 and an even number of stator teeth connected to the stator yoke 111. Each stator tooth includes a radially extending tooth body 112 and a tooth crown 113 connected to the distal end of the tooth body 112. The tooth crown 113 includes two pole shoes, which extend toward either side of the corresponding tooth body 112 in the direction of rotation of the rotor 2.

[0060] The rotor 2 cooperates with the stator 1 and is suitable for rotating relative to the stator 1 , and the number of poles of the rotor 2 is three times the number of teeth of the stator 1 .

[0061] The single-phase brushless DC motor 104 provided by the embodiment of the first aspect of the present invention has a stator 1 with a pole number of N (N is an even number), a rotor 2 with a pole number of 3N (i.e., 3 times N), and the 2N (i.e., 2 times N) pole shoes of the stator 1 act as magnetic field modulators. Through the above design, the number of pole pairs of the stator 1 and the rotor 2 is unequal, and the rotor magnetic field, after being modulated, can generate more operating harmonics when interacting with the stator magnetic field, thereby achieving the effect of torque amplification of the vernier permanent magnet motor, increasing the output torque of the motor, and improving the motor's operating efficiency. At the same time, the above design makes the harmonic content in the motor's back electromotive force lower, the waveform more sinusoidal, the motor operation more stable, and the torque fluctuation smaller, which is conducive to improving the vibration and noise performance of the motor.

[0062] Specifically, in the present application, the pole shoes of the stator 1 serve as modulation units and play a role in magnetic field modulation. The number of teeth of the stator 1 is N, and there are two left and right pole shoes on each tooth body 112, then the number of pole shoes is 2N, that is, the number of modulation units is 2N. Since the motor is a single-phase motor, the number of pole pairs of the stator 1 is N / 2 (i.e., half of N), and the number of pole pairs of the rotor 2 is 3N / 2 (i.e., half of 3N), and the number of pole pairs of the stator 1 and the number of pole pairs of the rotor 2 are not equal. However, the sum of the number of pole pairs of the stator 1 and the number of pole pairs of the rotor 2 is equal to the number of modulation units. Therefore, after passing through the modulation unit, the rotor magnetic field can interact with the stator magnetic field to generate torque, thereby realizing the magnetic field modulation torque amplification effect. After modulation, the fundamental wave content of the motor's no-load back electromotive force is higher, which is beneficial to increase the output torque of the motor and improve the motor's operating efficiency. In addition, the harmonic content in the back EMF after modulation is also lower, and the waveform is more sinusoidal, making the motor run more smoothly and the torque fluctuation smaller, which is beneficial to improving the vibration and noise performance of the motor.

[0063] In some embodiments, further, a groove 1131 is provided at a position of the tooth crown 113 facing the end surface of the rotor 2 and opposite to the tooth body 112, such as Figure 1 and Figure 2 As shown, the groove 1131 is located between the two pole pieces.

[0064] Providing a groove 1131 on the side of the tooth crown 113 close to the air gap can increase the magnetic resistance of the leakage magnetic circuit, reduce the inter-pole leakage magnetic flux, thereby increasing the output power of the motor and improving the utilization rate of the permanent magnet 22.

[0065] In some embodiments, the cross section of the groove 1131 is symmetrically arranged relative to the center line of the cross section of the tooth body 112, such as Figure 1 and Figure 2 shown.

[0066] The cross section of the groove 1131 is symmetrically arranged with respect to the center line of the cross section of the tooth body 112 , so that the structure of the stator core 11 is more regular and is easy to process and shape.

[0067] It is understood that, in this application, the center line of the cross section of the tooth body 112 refers to a straight line that intersects the central axis of the stator yoke 111 perpendicularly and extends along the radial direction of the stator yoke 111 and bisects the cross section of the tooth body 112 .

[0068] In other embodiments, the cross section of the groove 1131 is asymmetrically arranged relative to the center line of the cross section of the tooth body 112, such as Figure 5 shown.

[0069] The asymmetric cross-section of groove 1131 relative to the centerline of tooth body 112 creates a certain offset angle between the stator and rotor magnetic fields, thereby generating a certain starting angle during motor startup. This avoids dead spots, enabling self-starting and resolving the dead spot issue with single-phase motors. Furthermore, the asymmetric structure of groove 1131 provides rotor 2 with varying bidirectional starting capabilities, making it particularly suitable for applications requiring different bidirectional starting capabilities, such as power tools and window lifts.

[0070] Furthermore, the two ends of the cross section of the groove 1131 along the rotation direction of the rotor 2 are respectively marked as the first end and the second end, and the distance between the first end and the center line of the cross section of the tooth body 112 is greater or smaller than the distance between the second end and the center line of the cross section of the tooth body 112, as shown in FIG. Figure 5 shown.

[0071] This design can make the center line of the stator magnetic field and the center line of the rotor magnetic field not coincide with each other, thereby generating a certain starting angle when the motor starts, thereby avoiding the dead point position and achieving starting.

[0072] In some embodiments, specifically, the cross section of the groove 1131 is U-shaped, such as Figure 1 and Figure 2 Therefore, the structure is simple and easy to process and shape.

[0073] In other embodiments, the cross-section of the groove 1131 is V-shaped or arc-shaped, which facilitates the formation of a non-uniform air gap between the stator 1 and the rotor 2, helps avoid dead points, facilitates motor starting, and has a simple structure and is easy to process and form.

[0074] Furthermore, the width of the groove 1131 along the rotation direction of the rotor 2 is greater than the width of the tooth body 112 along the rotation direction of the rotor 2, as shown in FIG. Figure 1 、 Figure 5 and Figure 6 shown.

[0075] Such a design, on the one hand, is conducive to further increasing the magnetic resistance of the leakage magnetic circuit, further reducing the inter-pole leakage magnetic field, thereby further improving the output power of the motor and further improving the utilization rate of the permanent magnet 22; on the other hand, by controlling the position of the circumferential ends of the groove 1131, it is convenient for the two pole shoes on both sides of the same tooth body 112 to form an asymmetric structure, and then form an asymmetric air gap structure between the stator 1 and the rotor 2, which will make the centers of the stator magnetic field and the rotor magnetic field not coincide, thereby realizing motor starting.

[0076] Of course, the width of the groove 1131 along the rotation direction of the rotor 2 may also be equal to or smaller than the width of the tooth body 112 along the rotation direction of the rotor 2 .

[0077] In some embodiments, further, the distance between the pole shoe and the rotor 2 varies along the circumference of the rotor 2, so that a non-uniform air gap is formed between the stator 1 and the rotor 2, such as Figure 6 shown.

[0078] By controlling the spacing between the pole shoes and the rotor 2, a non-uniform air gap is created between the stator 1 and the rotor 2, helping to avoid dead spots and facilitate motor startup. Furthermore, the unequal air gaps between each pole shoe and the rotor 2 reduce the motor's equivalent air gap, enabling startup while maintaining high output performance.

[0079] In other embodiments, the distance between the pole shoe and the rotor 2 remains constant along the circumference of the rotor 2, such as Figure 1 and Figure 5 As shown, an air gap of equal thickness is formed between the pole shoe and the rotor 2, which is beneficial to reducing motor vibration and noise, making the motor run more smoothly, and enhancing the stability of motor starting.

[0080] In some embodiments, the two pole shoes of the same stator tooth 1 are respectively recorded as the first pole shoe 1132 and the second pole shoe 1133. The first pole shoe 1132 and the second pole shoe 1133 form an asymmetric structure with respect to the mid-vertical plane of the tooth body 112 of the same stator tooth 1, such as Figure 5 and Figure 6 As shown, the mid-vertical plane passes through the central axis of the stator yoke 111 .

[0081] The asymmetric design of the first pole shoe 1132 and the second pole shoe 1133 can generate a certain offset angle between the stator magnetic field and the rotor magnetic field, thereby realizing self-starting of the single-phase motor and solving the starting dead point problem of the single-phase motor.

[0082] It is understood that, in this application, the mid-vertical plane of the tooth body 112 refers to a plane passing through the central axis of the stator yoke 111 and perpendicularly bisecting the tooth body 112. The projection of the mid-vertical plane on the cross section of the tooth body 112 is the centerline of the cross section of the tooth body 112.

[0083] In other embodiments, the first pole shoe 1132 and the second pole shoe 1133 of the same stator tooth 1 may also be symmetrically arranged about the vertical plane of the corresponding tooth body 112, such as Figure 1 and Figure 2 This is beneficial to simplifying the structure of the stator core 11, facilitating processing and forming, and also facilitating forming symmetrical air gaps of equal thickness, thereby reducing motor vibration and noise, making the motor run more smoothly, and enhancing the stability of the motor startup.

[0084] In one embodiment, the length of the surface of the first pole shoe 1132 facing the rotor 2 along the rotation direction of the rotor 2 is less than the length of the surface of the second pole shoe 1133 facing the rotor 2 along the rotation direction of the rotor 2. Figure 5 shown.

[0085] The surface of the pole shoe facing the rotor 2 is called the working surface of the pole shoe (or the pole face of the pole shoe). The circumferential lengths of the working surfaces of the first pole shoe 1132 and the second pole shoe 1133 of the same stator tooth 1 are unequal, forming an asymmetric design. This also creates an asymmetric air gap structure between the stator 1 and rotor 2. This prevents the centers of the stator magnetic field from coinciding with the rotor magnetic field, creating a certain offset angle between the stator and rotor magnetic fields, thereby enabling self-starting of the motor.

[0086] In one embodiment, the area of ​​the surface of the first pole shoe 1132 facing the rotor 2 is smaller than the area of ​​the surface of the second pole shoe 1133 facing the rotor 2 .

[0087] The working surfaces of the first pole shoe 1132 and the second pole shoe 1133 of the same stator tooth are unequal in area, forming an asymmetric design. This also creates an asymmetric air gap structure between the stator 1 and the rotor 2. This prevents the centers of the stator magnetic field and the rotor magnetic field from coinciding, creating a certain offset angle between the stator and rotor magnetic fields, thereby enabling self-starting of the motor.

[0088] In one embodiment, the distance between the surface of the first pole shoe 1132 facing the rotor 2 and the central axis of the stator yoke 111 is recorded as a first distance, and the distance between the surface of the second pole shoe 1133 facing the rotor 2 and the central axis of the stator yoke 111 is recorded as a second distance. At least one of the first distance and the second distance gradually decreases or gradually increases along the rotation direction of the rotor 2, such as Figure 6 shown.

[0089] The distance between the working surface of the pole shoe and the central axis of the stator yoke 111 gradually increases or decreases, facilitating the creation of an air gap of non-uniform thickness between the pole shoe and the permanent magnet 22 of the rotor 2. This helps avoid dead points and facilitates motor starting. Furthermore, the permanent magnet 22 of the rotor 2 can have a regular, uniform thickness, simplifying the structure of the rotor 2. This also facilitates the formation of unequal air gaps between each pole shoe and the rotor 2, reducing the motor's equivalent air gap and enabling high output performance while achieving startup.

[0090] In one embodiment, at least one of the radial thickness of the first pole shoe 1132 and the radial thickness of the second pole shoe 1133 gradually decreases in a direction away from the corresponding tooth body 112. Figure 1 、 Figure 5 and Figure 6 shown.

[0091] The radial thickness of the pole shoe gradually decreases in the direction away from the corresponding tooth body 112 (i.e., the tooth body 112 connected to the pole shoe), so that the magnetic resistance of the pole shoe gradually increases in the direction away from the corresponding tooth body 112. Such a design can improve the air gap magnetic field waveform, making the waveform smoother, thereby making the motor run more smoothly and start more reliably.

[0092] In any of the above embodiments, the rotor 2 includes a rotor yoke 21 and a permanent magnet 22. Figure 1 As shown, the radial thickness of the permanent magnet 22 gradually decreases or increases along the rotation direction of the rotor 2 .

[0093] The radial thickness of the permanent magnets 22 gradually decreases or increases along the rotational direction of the rotor 2. This facilitates the creation of an air gap of non-uniform thickness between the pole shoes and the permanent magnets 22 of the rotor 2, helping to avoid dead spots and facilitating motor startup. Furthermore, the working surface of the pole shoes can be an arc surface concentric with the stator yoke 111, simplifying the structure of the stator 1. This also facilitates the formation of unequal air gaps between each pole shoe and the rotor 2, resulting in a smaller equivalent air gap for the motor, enabling startup while still maintaining high output performance.

[0094] In some embodiments, the rotor 2 is sleeved on the inner side of the stator 1 to form an inner rotor 2 motor.

[0095] In other embodiments, the rotor 2 is sleeved on the outside of the stator 1, such as Figure 1 、 Figure 5 and Figure 6 As shown, an outer rotor 2 motor is formed.

[0096] like Figure 7 As shown, the electrical device 100 provided by the embodiment of the second aspect of the present invention includes: a device body 102 and a single-phase brushless DC motor 104 as any one of the embodiments of the first aspect. The single-phase brushless DC motor 104 is connected to the device body 102.

[0097] The electrical device 100 provided in the embodiment of the second aspect of the present invention includes the single-phase brushless DC motor 104 of any one of the embodiments of the first aspect, and thus has all the beneficial effects of any of the above embodiments, which will not be repeated here.

[0098] In the above embodiment, the electrical device 100 may be, but is not limited to, a water pump, a refrigerator fan, a computer or other low-power device.

[0099] Specifically, the electrical device 100 is a water pump, the device body 102 includes an impeller, and the single-phase brushless DC motor 104 is connected to the impeller.

[0100] The electrical device 100 is a refrigerator or a refrigerator fan. The device body 102 includes an impeller, and a single-phase brushless DC motor 104 is connected to the impeller.

[0101] The electrical device 100 is a computer, and the device body 102 includes an impeller, and a single-phase brushless DC motor 104 is connected to the impeller.

[0102] Several specific examples are described in detail below.

[0103] Specific Example 1

[0104] Figure 1 It is a schematic diagram of a first specific example of the present invention.

[0105] In this example, the single-phase brushless DC motor provided by the present invention includes a stator 1 and a rotor 2 that rotates relative to the stator 1. The stator 1 includes a stator core 11 and a winding 12 wound on the stator core 11. In the winding 12, the current directions of the conductors in the same slot are the same, and the current directions of the conductors in adjacent slots are opposite. The stator core 11 includes a stator yoke 111, a tooth body 112 (or stator tooth body) extending radially toward the air gap side from the annular stator yoke 111, and a tooth crown 113 formed at the end of the tooth body, and the number N of stator teeth is an even number. A groove 1131 is provided on the tooth crown 113 at a position close to the air gap side and opposite to the tooth body 112, and the width of the groove 1131 can be greater than the width of the tooth body 112. On the left and right sides of the groove 1131, there are stator pole shoes (including a first pole shoe 1132 and a second pole shoe 1133) extending in the circumferential direction. The rotor 2 includes an annular rotor yoke 21 and a plurality of permanent magnets 22 , and adjacent permanent magnets have opposite polarities.

[0106] Among them, the number of rotor poles is three times the number of stator poles, that is, 3N.

[0107] The present invention is a brushless DC motor, which uses a DC power supply to power the windings of the above-mentioned motor, and the current is commutated once every 180° electrical angle, that is, once every (120 / N)° mechanical angle, so that the stator magnetic field and the rotor magnetic field always maintain an electrical angle of about 90° in space, thereby driving the motor to rotate continuously.

[0108] In the present invention, the stator pole shoe serves as a modulation unit and plays a role in magnetic field modulation. The number of stator teeth is N, and there are two stator pole shoes on the left and right sides of each tooth. Then the number of stator pole shoes is 2N, that is, the number of modulation units is 2N. Since the motor is a single-phase motor, the number of stator pole pairs is N / 2, while the number of rotor pole pairs is 3N / 2, and the number of stator and rotor pole pairs is not equal. However, the sum of the number of stator pole pairs and the number of rotor pole pairs is equal to the number of modulation units. Therefore, after passing through the modulation unit, the rotor magnetic field can interact with the stator magnetic field to generate torque, realizing the magnetic field modulation torque amplification effect. After modulation, the fundamental wave content of the motor's no-load back electromotive force is higher, which is beneficial to increasing the motor's output torque and improving the motor's operating efficiency. In addition, the harmonic content in the back electromotive force after modulation is also lower, and the waveform is more sinusoidal, making the motor run more smoothly and the torque fluctuation smaller, which is beneficial to improving the motor's vibration and noise performance.

[0109] However, since the rotor has more poles, the inter-pole magnetic leakage is large. In order to reduce this part of the magnetic leakage, improve the motor output, and enhance the utilization rate of the permanent magnet, the present invention provides a groove on the stator tooth crown close to the air gap side, thereby reducing the inter-pole magnetic leakage by increasing the magnetic resistance of the leakage magnetic circuit. Figure 2 This is the magnetic flux distribution diagram of the motor at no load. It can be seen that the inclusion of the grooves reduces the magnetic flux leakage between the permanent magnet poles. Furthermore, the grooves are located as an extension of the stator teeth, and their width can be greater than the stator teeth.

[0110] Furthermore, Figure 3 A comparison diagram of the back EMF waveforms of the single-phase brushless DC motor of the present invention and the single-phase brushless DC motor in the prior art at no load is given. Figure 4 The following figure compares the Fourier decomposition results of the no-load back EMF of the two motors. As can be seen, the above design results in a higher fundamental content in the no-load back EMF of the motor in the present invention, lower harmonic distortion, and a more sinusoidal waveform. This helps increase the motor's output torque and reduce torque ripple.

[0111] Specific Example 2

[0112] Based on the specific example 1, the cross section of the stator groove 1131 is asymmetric with respect to the center line of the stator tooth body. Figure 5 As shown in the figure, the distance from one end of the stator slot to the centerline of the tooth body is d1, and the distance from the other end of the slot to the centerline of the tooth body is d2, with d1 ≠ d2. This design prevents the stator magnetic field centerline from coinciding with the rotor magnetic field centerline, creating a certain starting angle when the motor starts, thus avoiding the dead point position and achieving startup.

[0113] In the above embodiment, the cross section of the groove may be V-shaped or arc-shaped.

[0114] Furthermore, the first pole shoe 1132 and the second pole shoe 1133 are asymmetrical about the center line of the stator tooth body. Similarly, a certain offset angle can be generated between the stator magnetic field and the rotor magnetic field, thereby achieving motor starting.

[0115] Specific Example 3

[0116] Based on the specific example 2, further, as Figure 6 As shown, the distances from the working surfaces of the first pole shoe 1132 and the second pole shoe 1133 to the stator center are unequal along the circumferential direction. Specifically, the outer diameter of the first pole shoe 1132 gradually decreases from its edge to the edge of the groove 1131, and the outer diameter of the second pole shoe 1133 gradually decreases from the edge of the groove 1131 to the edge of the pole shoe.

[0117] Similarly, the thickness of the first pole piece 1132 and the second pole piece 1133 may be unequal, or the lengths along the circumferential direction may be different.

[0118] This design creates an asymmetric air gap structure, preventing the stator and rotor magnetic field centers from aligning, thus enabling starting. Furthermore, by providing unequal air gaps around each pole shoe, the motor's equivalent air gap is reduced, enabling starting while maintaining high output performance.

[0119] Similarly, the thickness of each permanent magnet in the rotor gradually decreases or increases along the direction of rotation of the rotor. Through this design, the stator magnetic field and the rotor magnetic field center line can also be offset, thereby achieving starting.

[0120] In addition, the above examples are all outer rotor single-phase motors, but the structure is also applicable to inner rotor single-phase motors.

[0121] In summary, the single-phase brushless DC motor of the present invention can increase the average torque of the motor and reduce inter-pole magnetic leakage, thereby further improving the output performance of the motor and enhancing the operating efficiency of the motor.

[0122] In the present invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "plurality" refers to two or more, unless expressly limited otherwise. Terms such as "installed," "connected," "connected," and "fixed" should be interpreted broadly. For example, "connected" can mean a fixed connection, a detachable connection, or an integral connection; "connected" can mean a direct connection or an indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0123] In the description of the present invention, it should be understood that the directions or positional relationships indicated by terms such as "up", "down", "left", "right", "front" and "back" are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0124] Throughout this specification, terms such as "one embodiment," "some embodiments," and "specific embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0125] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A single-phase brushless DC motor, characterized in that: include: A stator, the stator comprising a stator core and a winding wound around the stator core, the stator core comprising a stator yoke and an even number of stator teeth connected to the stator yoke, each stator tooth comprising a tooth body extending radially and a tooth crown connected to a distal end of the tooth body, the tooth crown comprising two pole shoes, the two pole shoes extending toward opposite sides of the corresponding tooth body in the direction of rotation of the rotor; and The rotor cooperates with the stator and is suitable for rotating relative to the stator, and the number of poles of the rotor is three times the number of teeth of the stator.

2. The single-phase brushless DC motor according to claim 1, characterized in that: A groove is provided at a position of the tooth crown facing the end surface of the rotor and opposite to the tooth body, and the groove is located between the two pole shoes.

3. The single-phase brushless DC motor according to claim 2, characterized in that: The cross section of the groove is symmetrically arranged relative to the center line of the cross section of the tooth body; or The cross section of the groove is asymmetrically arranged relative to a center line of the cross section of the tooth body.

4. The single-phase brushless DC motor according to claim 2, characterized in that: The two ends of the cross section of the groove along the rotation direction of the rotor are respectively marked as the first end and the second end, and the distance between the first end and the center line of the cross section of the tooth body is greater than or less than the distance between the second end and the center line of the cross section of the tooth body.

5. The single-phase brushless DC motor according to claim 2, characterized in that: The cross section of the groove is U-shaped, V-shaped or arc-shaped.

6. The single-phase brushless DC motor according to claim 2, characterized in that: The width of the groove along the rotation direction of the rotor is greater than the width of the tooth body along the rotation direction of the rotor.

7. The single-phase brushless DC motor according to any one of claims 1 to 6, characterized in that: The distance between the pole shoes and the rotor varies along the circumference of the rotor, so as to form a non-uniform air gap between the stator and the rotor.

8. The single-phase brushless DC motor according to any one of claims 1 to 6, characterized in that: The two pole shoes of the same stator tooth are respectively recorded as a first pole shoe and a second pole shoe. The first pole shoe and the second pole shoe form an asymmetric structure with respect to the median vertical plane of the tooth body of the same stator tooth, and the median vertical plane passes through the central axis of the stator yoke.

9. The single-phase brushless DC motor according to claim 8, characterized in that: The length of the surface of the first pole shoe facing the rotor along the rotation direction of the rotor is smaller than or larger than the length of the surface of the second pole shoe facing the rotor along the rotation direction of the rotor; and / or An area of ​​a surface of the first pole shoe facing the rotor is smaller than or larger than an area of ​​a surface of the second pole shoe facing the rotor.

10. The single-phase brushless DC motor according to claim 8, characterized in that: The distance between the surface of the first pole shoe facing the rotor and the central axis of the stator yoke is recorded as a first distance, and the distance between the surface of the second pole shoe facing the rotor and the central axis of the stator yoke is recorded as a second distance; at least one of the first distance and the second distance gradually decreases or gradually increases along the rotation direction of the rotor; and / or At least one of the radial thickness of the first pole shoe and the radial thickness of the second pole shoe gradually decreases in a direction away from the corresponding tooth body.

11. The single-phase brushless DC motor according to any one of claims 1 to 6, characterized in that: The rotor includes a rotor yoke and a permanent magnet; The radial thickness of the permanent magnet gradually decreases or increases along the rotation direction of the rotor.

12. The single-phase brushless DC motor according to any one of claims 1 to 6, characterized in that: The rotor is sleeved on the inner side of the stator; or The rotor is sleeved on the outer side of the stator.

13. An electrical device, characterized in that: include: Equipment body; and The single-phase brushless DC motor according to any one of claims 1 to 12, connected to the device main body.

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