Low-noise position-sensorless motor for small household appliances

Abstract

The utility model relates to the technical field of motors, in particular to a low-noise sensorless motor for small household appliances, which comprises a stator assembly and a rotor assembly arranged in a stator. The motor is an eight-pole twelve-slot motor; the stator assembly comprises a stator iron core, the outer diameter of the stator iron core is 70-150 mm, and the ratio of the inner diameter to the outer diameter of the stator iron core is 0.5-0.7; the rotor assembly comprises a rotor iron core and a rotor permanent magnet; the d-axis surface of the rotor iron core comprises at least one section of eccentric arc; according to the technical scheme, the motor rotor has the advantages that noise is reduced, cost is reduced after a position sensor does not need to be arranged, and the reliability of the motor is improved.

Description

Technical Field

[0001] The utility model relates to a motor, in particular to a low-noise position sensor-free motor for small household appliances. Background Art

[0002] In the application field of small household appliances, such as food processors and coffee machines, their drive motors need to have the ability to operate in a wide speed range, that is, the motor has a maximum torque output at a low speed of about 500rpm (revolutions per minute), and the motor can also run at about 20,000rpm and have a constant power output.

[0003] However, the DC permanent magnet brushless motor driven by square wave current generated by the commonly used three-phase six-step method is difficult to meet this requirement. Therefore, it is necessary to use a permanent magnet synchronous motor driven by sinusoidal current generated by space vector control. This motor can run at maximum torque at low speed and can also run at high speed using weak magnetic field. Since this kind of small household appliance is usually used in occasions where people come into contact, low noise is one of the important indicators of its performance assessment, especially it should not produce harsh high-frequency whistling during operation to avoid adverse effects on user experience and physical and mental health.

[0004] In addition, in order to achieve stable operation at low speed and high torque, traditional small household appliance motors of this type usually use position sensors to collect rotor position signals in real time to drive the normal operation of the motor. Commonly used position sensors include Hall elements, rotary encoders, etc. These position sensors not only increase the cost of the motor, but are also prone to damage and failure, thereby reducing the reliability of the motor.

[0005] Therefore, position sensorless control methods, especially high-frequency injection, have become an urgent development direction in this type of motor drive method. Utility Model Content

[0006] In order to solve the problems in the related art, the present application provides a low-noise position sensorless motor for small household appliances, which solves the problem that the motor has high noise and the position sensor installed on the motor is easily damaged and fails, thereby increasing the cost of the motor and reducing reliability.

[0007] The technical solution is as follows:

[0008] A low-noise position sensorless motor for small household appliances comprises a stator assembly and a rotor assembly arranged in the stator assembly; the motor is an eight-pole twelve-slot motor; the stator assembly comprises a stator core, the outer diameter of the stator core is 70mm-150mm, and the ratio of the inner diameter to the outer diameter of the stator core is 0.5-0.7; the rotor assembly comprises a rotor core and a rotor permanent magnet; the d-axis surface of the rotor core comprises at least one eccentric arc; the rotor permanent magnet is embedded in the rotor core.

[0009] Through the above technical solution, by setting up the eight-stage twelve-slot motor in coordination, the harmonic frequency of the radial electromagnetic force wave in the motor air gap can be greatly reduced, thereby greatly reducing the motor noise, especially the high-frequency howling; by controlling the ratio of the inner diameter to the outer diameter of the stator core to be between 0.5-0.7, that is, controlling the stator split ratio to be between 0.5-0.7, this can ensure that the motor is in the best electromagnetic output performance when in use;

[0010] By making the d-axis surface of the rotor core include at least one eccentric arc, it can be ensured that the motor back electromotive force is a sine wave and its total harmonic content is less than 5%, and the cogging torque is reduced, thereby reducing the motor torque fluctuation and reducing the vibration noise of the motor.

[0011] Preferably, the eight rotor permanent magnets are evenly arranged along the circumference of the rotor core; and the twelve teeth are evenly arranged along the circumference of the stator core.

[0012] Preferably, the d-axis surface of the rotor core includes eight eccentric arcs, the central axes of the eight eccentric arcs are at the same distance from the center of the rotor assembly, the eight eccentric arcs are arranged in sequence along the circumference of the rotor core, and there is a connecting section between two adjacent eccentric arcs; the rotor permanent magnets and the eccentric arcs are arranged in a one-to-one correspondence.

[0013] Through the above technical solution, the motor is a position sensorless motor, and the salient pole ratio of the motor is greater than or equal to 1.2.

[0014] By embedding the rotor permanent magnets in the rotor core and the motor salient pole ratio being greater than or equal to 1.2, that is, the ratio of the q-axis inductance to the d-axis inductance being greater than or equal to 1.2, the motor can be controlled using a high-frequency injection sensorless control method, thereby omitting the method of controlling the motor by setting a position sensor in the motor, thereby reducing the motor investment cost and improving the reliability of the motor.

[0015] Preferably, coil windings are respectively wound along the outer circumferences of the twelve teeth.

[0016] Preferably, the eight rotor permanent magnets each include two magnetic steels, the two magnetic steels of each rotor permanent magnet are symmetrically distributed along the central axis of the corresponding eccentric arc, and the angle between the two magnetic steels of each rotor permanent magnet is greater than 90°.

[0017] Through the above technical solution, by providing two magnetic steels for each of the eight rotor permanent magnets and arranging them in a V-shape, the salient pole ratio of the motor can reach 1.33, so that the motor can meet the requirements of the high-frequency injection algorithm for the salient pole ratio of the motor, thereby achieving the need to control the motor through the high-frequency injection algorithm without installing a position sensor in the motor, thereby reducing the production cost of the motor and improving the reliability of the motor.

[0018] Preferably, the eight rotor permanent magnets each include a single-piece magnetic steel, and the width direction of the single-piece magnetic steel of each rotor permanent magnet is symmetrically distributed along the central axis of the corresponding eccentric arc.

[0019] Through the above technical solution, by arranging a single-piece magnetic steel in the eight rotor permanent magnets to form a straight line arrangement, the salient pole ratio of the motor can reach 1.29, so that the motor can meet the requirements of the high-frequency injection algorithm for the salient pole ratio of the motor, thereby achieving the need to control the motor through a high-frequency injection algorithm without installing a position sensor in the motor, thereby reducing the production cost of the motor and improving the reliability of the motor.

[0020] Preferably, a non-conductive and non-magnetic sheath is provided on the surface of the rotor core.

[0021] By selecting a non-conductive and non-magnetic material to make the sheath and fastening it to the outer surface of the rotor core, the centrifugal force can be prevented from damaging the rotor when the rotor rotates at high speed. The non-conductive nature of the sheath can reduce the eddy current loss of the sheath, reduce rotor heat generation, and improve motor performance, thereby improving the reliability of the motor and extending the service life of the motor. In addition, when the motor runs at 20,000 rpm, the loss of the motor is reduced by about 130 W compared to a motor with a conductive sheath, which helps to extend the service life of the motor, thereby improving the reliability and stability of the motor and reducing the operating cost of the motor.

[0022] In summary, the beneficial effect of a low-noise position sensorless motor for small household appliances is that the coordination of the eight-stage twelve-slot arrangement in the motor can greatly reduce the number of harmonics of the radial electromagnetic force wave in the motor air gap, thereby greatly reducing the motor noise, especially the high-frequency howling; by controlling the ratio of the inner diameter to the outer diameter of the stator core to be between 0.5 and 0.7, that is, controlling the stator split ratio to be between 0.5 and 0.7, this can ensure that the motor is in the optimal electromagnetic output performance when in use;

[0023] By making the d-axis surface of the rotor core include at least one eccentric arc, it can be ensured that the motor back electromotive force is a sine wave and its total harmonic content is less than 5%, and the cogging torque is reduced, thereby reducing the motor torque fluctuation, thereby reducing the vibration noise of the motor;

[0024] By setting the rotor permanent magnet in an embedded manner in the rotor core, and the motor salient pole ratio is greater than or equal to 1.2, that is, the ratio of the q-axis inductance to the d-axis inductance is greater than or equal to 1.2, the motor can be controlled by a high-frequency injection non-sensing control method, thereby omitting the method of controlling the motor by setting a position sensor in the motor, thereby reducing the motor investment cost and improving the reliability of the motor;

[0025] By selecting a non-conductive and non-magnetic material to make the sheath and fastening it to the outer surface of the rotor core, the centrifugal force can be prevented from damaging the rotor when the rotor rotates at high speed. The non-conductive nature of the sheath can reduce the eddy current loss of the sheath, reduce rotor heat generation, and improve motor performance, thereby improving the reliability of the motor and extending the service life of the motor. In addition, when the motor runs at 20,000 rpm, the loss of the motor is reduced by about 130 W compared to a motor with a conductive sheath, which helps to extend the service life of the motor, thereby improving the reliability and stability of the motor and reducing the operating cost of the motor.

[0026] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present utility model, and together with the description, are used to explain the principles of the present utility model.

[0028] Figure 1 It is a schematic diagram of the structure of the utility model;

[0029] Figure 2 It is a schematic diagram of the explosion structure of the utility model;

[0030] Figure 3 It is a top view of the stator core in the utility model;

[0031] Figure 4 This is a schematic diagram of the installation of the permanent magnet in Example 1 of the utility model;

[0032] Figure 5 This is a schematic diagram of the installation of the permanent magnet in Example 2 of the utility model;

[0033] Figure 6 It is a top view of the rotor core in the utility model;

[0034] Figure 7 This is a comparison table of radial stress for motors with different numbers of pole slots in the utility model;

[0035] Figure 8This is a comparison table of back electromotive force between the eccentric arc rotor and the full circle rotor in the utility model;

[0036] Fig. 9 A comparison table of harmonic orders between the eccentric arc rotor and the full circle rotor in the utility model;

[0037] Fig.10 This is a comparison table of the cogging torque between the eccentric arc rotor and the full circle rotor in the utility model;

[0038] In the figure, 1. rotor core; 2. rotor permanent magnet; 3. stator core; 4. coil winding; 5. sheath; 6. rotor shaft; 7. stator front end plate; 8. stator rear end plate; 9. motor front bearing; 10. motor rear bearing; 11. motor front end cover; 12. motor rear end cover; 13. motor casing. DETAILED DESCRIPTION

[0039] Here, exemplary embodiments will be described in detail, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the utility model. Instead, they are only examples of devices and methods consistent with some aspects of the utility model as detailed in the attached claims.

[0040] Embodiment 1:

[0041] As attached Figure 1-4 6-10, a low-noise position sensorless motor for small household appliances, the driving current of the motor is a sine wave current, including a stator assembly and a rotor assembly arranged in the stator assembly;

[0042] The motor is an eight-pole twelve-slot motor, with eight rotor permanent magnets 2 arranged in sequence along the circumference of the rotor core 1, and twelve teeth evenly arranged along the circumference of the stator core 3; the radial force wave harmonic order of the eight-pole twelve-slot electromagnetic structure is a multiple of 4, which is much less than the multiple of 2 of the ten-pole twelve-slot or fourteen-pole twelve-slot electromagnetic structure. Therefore, the eight-pole twelve-slot electromagnetic structure can greatly reduce the harmonic order of the motor radial force wave, thereby reducing the noise of the motor, especially the high-frequency howling.

[0043] The stator assembly includes a stator core 3, and coil windings 4 are respectively wound along the outer periphery of the twelve teeth; the ratio of the inner diameter to the outer diameter of the stator core 3 is 0.5-0.7, that is, the stator split ratio is controlled between 0.5-0.7, which can ensure that the motor is in the optimal electromagnetic output performance when in use; if the stator split ratio is greater than 0.7, the stator winding slot space is too small, the stator winding wire diameter is too thin and the internal resistance is too large, which will cause the motor copper loss to be too large and the efficiency to be low; if the stator split ratio is less than 0.5, the rotor outer diameter is too small, and the motor torque is too small and the output is insufficient; the outer diameter of the stator core 3 is 70mm-150mm, and the rated input power is 100W-3500W; the stator front end plate 7 and the stator rear end plate 8 are respectively arranged at both ends of the axis of the stator core 3.

[0044] The rotor assembly includes a rotor core 1 and a rotor permanent magnet 2, the rotor permanent magnet 2 is embedded in the rotor core 1, the motor is a position sensorless motor, and the salient pole ratio of the motor is greater than or equal to 1.2; the rotor permanent magnet 2 is embedded in the rotor core 1, and the motor salient pole ratio is greater than or equal to 1.2, that is, the ratio of the q-axis inductance to the d-axis inductance is greater than or equal to 1.2, so that the motor can be controlled by a high-frequency injection non-sensing control method, thereby omitting the method of controlling the motor by setting a position sensor in the motor, thereby reducing the motor investment cost and improving the reliability of the motor;

[0045] The d-axis surface of the rotor core 1 includes at least one eccentric arc, which can ensure that the motor back electromotive force is a sine wave and its total harmonic content is less than 5%, and reduce the cogging torque, thereby reducing the motor torque fluctuation, thereby reducing the vibration noise of the motor;

[0046] In this embodiment, as Figure 6 As shown, the d-axis surface of the rotor core 1 includes eight eccentric arcs, that is, the rotor d-axis is composed of eight eccentric arcs with an eccentric distance L1 and a radius R1; the central axes of the eight eccentric arcs have the same distance from the center of the rotor assembly, and the eight eccentric arcs are arranged in sequence along the circumference of the rotor core 1, and there is a connecting section between two adjacent eccentric arcs; the rotor permanent magnets 2 and the eccentric arcs are arranged in a one-to-one correspondence;

[0047] The eight rotor permanent magnets 2 each include two magnetic steels, and the two magnetic steels of each rotor permanent magnet 2 are symmetrically distributed along the central axis of the corresponding eccentric arc, and the angle between the two magnetic steels of each rotor permanent magnet 2 is greater than 90°; since the eight rotor permanent magnets 2 each include two magnetic steels, and the two magnetic steels are arranged in a V shape, the salient pole ratio of the motor can reach 1.33, so that the motor can meet the requirements of the high-frequency injection algorithm for the salient pole ratio of the motor, and then there is no need to install a position sensor in the motor, but the motor can be controlled by the high-frequency injection algorithm, thereby reducing the production cost of the motor and improving the reliability of the motor.

[0048] The outer surface of the rotor core 1 is adapted to be provided with a non-conductive and non-magnetic sheath 5; the material of the non-conductive and non-magnetic sheath 5 is such as carbon fiber, glass fiber, etc.; after the sheath 5 is made of a non-conductive and non-magnetic material and is securely arranged on the outer surface of the rotor core 1, when the rotor rotates at a high speed, the sheath 5 can prevent the centrifugal force from damaging the rotor due to its non-conductivity, and the non-conductivity of the sheath 5 can reduce the eddy current loss of the sheath 5, reduce the heat of the rotor, and improve the motor performance, thereby improving the reliability of the motor and extending the service life of the motor; in addition, when the motor runs at 20000rpm, the loss of the motor at this time is reduced by about 130W compared with the motor using the conductive sheath 5, which helps to extend the service life of the motor, thereby improving the reliability and stability of the motor and reducing the operating cost of the motor.

[0049] A matching rotor shaft 6 is arranged along the central axis of the rotor core 1. The device also includes a motor housing 13, a motor front end cover 11 and a motor rear end cover 12 which are matched and arranged at both ends of the motor housing 13; a motor front bearing 9 and a motor rear bearing 10 which are arranged in a rotational direction are respectively arranged in the motor front end cover 11 and the motor rear end cover 12, and the motor front bearing 9 and the motor rear bearing 10 are respectively sleeved on the rotor shaft 6, and the stator is matched and arranged in the motor housing 13 between the motor front bearing 9 and the motor rear bearing 10.

[0050] Embodiment 2:

[0051] As attached Figure 1-3 , 5-10, a low-noise position sensorless motor for small household appliances, the driving current of the motor is a sine wave current, including a stator assembly and a rotor assembly arranged in the stator assembly;

[0052] The motor is an eight-pole twelve-slot motor, with eight rotor permanent magnets 2 arranged in sequence along the circumference of the rotor core 1, and twelve teeth evenly arranged along the circumference of the stator core 3; the radial force wave harmonic order of the eight-pole twelve-slot electromagnetic structure is a multiple of 4, which is much less than the multiple of 2 of the ten-pole twelve-slot or fourteen-pole twelve-slot electromagnetic structure. Therefore, the eight-pole twelve-slot electromagnetic structure can greatly reduce the harmonic order of the motor radial force wave, thereby reducing the noise of the motor, especially the high-frequency howling.

[0053] The stator assembly includes a stator core 3 and a coil winding 4 wound on the stator core 3; the ratio of the inner diameter to the outer diameter of the stator core 3 is 0.5-0.7, that is, the stator split ratio is controlled between 0.5-0.7, which can ensure that the motor is in the optimal electromagnetic output performance when in use; if the stator split ratio is greater than 0.7, the stator winding slot space is too small, the stator winding wire diameter is too thin and the internal resistance is too large, which will cause the motor copper loss to be too large and the efficiency to be low; if the stator split ratio is less than 0.5, the rotor outer diameter is too small, and the motor torque is too small and the output is insufficient; the outer diameter of the stator core 3 is 70mm-150mm, and the rated input power is 100W-3500W; the stator front end plate 7 and the stator rear end plate 8 are respectively provided at both ends of the axis of the stator core 3.

[0054] The rotor assembly includes a rotor core 1 and a rotor permanent magnet 2, wherein the rotor permanent magnet 2 is embedded in the rotor core 1, and the salient pole ratio of the motor is greater than or equal to 1.2; the rotor permanent magnet 2 is embedded in the rotor core 1, the motor is a position sensorless motor, and the motor salient pole ratio is greater than or equal to 1.2, that is, the ratio of the q-axis inductance to the d-axis inductance is greater than or equal to 1.2, thereby enabling the motor to be controlled by a high-frequency injection non-sensing control method, thereby omitting the method of controlling the motor by setting a position sensor in the motor, thereby reducing the motor investment cost and improving the reliability of the motor;

[0055] The d-axis surface of the rotor core 1 includes at least one eccentric arc, which can ensure that the motor back electromotive force is a sine wave and its total harmonic content is less than 5%, and reduce the cogging torque, thereby reducing the motor torque fluctuation, thereby reducing the vibration noise of the motor;

[0056] In this embodiment, as Figure 6 As shown, the d-axis surface of the rotor core 1 includes eight eccentric arcs, that is, the rotor d-axis is composed of eight eccentric arcs with an eccentric distance L1 and a radius R1; the central axes of the eight eccentric arcs have the same distance from the center of the rotor assembly, and the eight eccentric arcs are arranged in sequence along the circumference of the rotor core 1, and there is a connecting section between two adjacent eccentric arcs; the rotor permanent magnets 2 and the eccentric arcs are arranged in a one-to-one correspondence;

[0057] The eight rotor permanent magnets 2 all include a single-piece magnetic steel, and the width direction of the single-piece magnetic steel of each rotor permanent magnet 2 is symmetrically distributed along the central axis of the corresponding eccentric arc; since the eight rotor permanent magnets all include a single-piece magnetic steel, and each single-piece magnetic steel is arranged in a straight line, the salient pole ratio of the motor can reach 1.29, so that the motor can meet the requirements of the high-frequency injection algorithm for the salient pole ratio of the motor, and then there is no need to install a position sensor in the motor, but the motor can be controlled by the high-frequency injection algorithm, thereby reducing the production cost of the motor and improving the reliability of the motor.

[0058] The outer surface of the rotor core 1 is adapted to be provided with a non-conductive and non-magnetic sheath 5; the material of the non-conductive and non-magnetic sheath 5 is such as carbon fiber, glass fiber, etc.; after the sheath 5 is made of a non-conductive and non-magnetic material and is securely arranged on the outer surface of the rotor core 1, when the rotor rotates at a high speed, the sheath 5 can prevent the centrifugal force from damaging the rotor due to its non-conductivity, and the non-conductivity of the sheath 5 can reduce the eddy current loss of the sheath 5, reduce the heat of the rotor, and improve the motor performance, thereby improving the reliability of the motor and extending the service life of the motor; in addition, when the motor runs at 20000rpm, the loss of the motor at this time is reduced by about 130W compared with the motor using the conductive sheath 5, which helps to extend the service life of the motor, thereby improving the reliability and stability of the motor and reducing the operating cost of the motor.

[0059] A matching rotor shaft 6 is arranged along the central axis of the rotor core 1. The device also includes a motor housing 13, a motor front end cover 11 and a motor rear end cover 12 which are matched and arranged at both ends of the motor housing 13; a motor front bearing 9 and a motor rear bearing 10 which are arranged in a rotational direction are respectively arranged in the motor front end cover 11 and the motor rear end cover 12, and the motor front bearing 9 and the motor rear bearing 10 are respectively sleeved on the rotor shaft 6, and the stator is matched and arranged in the motor housing 13 between the motor front bearing 9 and the motor rear bearing 10.

[0060] Working principle: After the stator and rotor are assembled into a motor, the permanent magnet in the rotor is embedded and the salient pole ratio of the motor is greater than or equal to 1.2, so that the motor can be controlled by a high-frequency injection sensorless control method, thereby reducing costs and improving reliability; and the motor's eight-pole and twelve-slot setting and the non-circular outer surface of the rotor can greatly reduce the noise of the motor.

[0061] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the utility model herein. This application is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary technical means in the art that are not applicable to the present invention. The specification and examples are to be regarded as exemplary only, and the true scope and spirit of the present invention are indicated by the appended claims.

[0062] It should be understood that the present invention is not limited to the structures described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A low-noise position sensorless motor for small household appliances, comprising a stator assembly and a rotor assembly arranged in the stator assembly; characterized in that: The motor is an eight-pole twelve-slot motor; the stator assembly includes a stator core, the outer diameter of the stator core is 70mm-150mm, and the ratio of the inner diameter to the outer diameter of the stator core is 0.5-0.7; the rotor assembly includes a rotor core and a rotor permanent magnet; the d-axis surface of the rotor core includes at least one eccentric arc; the rotor permanent magnet is embedded in the rotor core.

2. A low-noise position sensorless motor for small household appliances according to claim 1, characterized in that: Eight rotor permanent magnets are evenly arranged along the circumference of the rotor core; and twelve teeth are evenly arranged along the circumference of the stator core.

3. A low-noise position sensorless motor for small household appliances according to claim 2, characterized in that: The d-axis surface of the rotor core includes eight eccentric arcs, the central axes of the eight eccentric arcs are at the same distance from the center of the rotor assembly, the eight eccentric arcs are arranged in sequence along the circumference of the rotor core, and there is a connecting section between two adjacent eccentric arcs; the rotor permanent magnets and the eccentric arcs are arranged in a one-to-one correspondence.

4. A low-noise position sensorless motor for small household appliances according to claim 1, characterized in that: The motor is a position sensorless motor, and the salient pole ratio of the motor is greater than or equal to 1.

2.

5. A low-noise position sensorless motor for small household appliances according to claim 3, characterized in that: The eight rotor permanent magnets each include two magnetic steels, the two magnetic steels of each rotor permanent magnet are symmetrically distributed along the central axis of the corresponding eccentric arc, and the angle between the two magnetic steels of each rotor permanent magnet is greater than 90°.

6. A low-noise position sensorless motor for small household appliances according to claim 3, characterized in that: The eight rotor permanent magnets all include a single-piece magnetic steel, and the width direction of the single-piece magnetic steel of each rotor permanent magnet is symmetrically distributed along the central axis of the corresponding eccentric arc.

7. A low-noise position sensorless motor for small household appliances according to claim 2, characterized in that: Coil windings are respectively wound around the outer circumferences of the twelve teeth.

8. A low-noise position sensorless motor for small household appliances according to claim 1, characterized in that: The surface of the rotor core is adapted to be provided with a non-conductive and non-magnetic sheath.

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