Motor and oral cavity cleaning equipment

Abstract

The invention relates to a motor and an oral cavity cleaning device. The motor comprises a rotor assembly and a stator assembly, the rotor assembly is provided with a rotor shaft extending along a rotating axis and four magnets sequentially arranged on the rotor shaft at equal intervals in the circumferential direction, and every two adjacent magnets are opposite in magnetism; the stator assembly is provided with four stator core bodies which surround the rotor assembly and are sequentially arranged at equal intervals in the circumferential direction, each stator core body is constructed to be a mounting winding, and each winding is matched with two adjacent magnets; in at least one plane perpendicular to the rotating axis of the rotor assembly, the intersection point of the rotating axis and the plane serves as the circle center, and the range of the central angle of the outer arc section, close to the stator core body, of the magnet and the central angle of the inner arc section, close to the magnet, of the stator core body ranges from 71 degrees to 81 degrees. By means of the design, in the swing period of the rotor assembly, the constant torque interval is located in the area with the small cogging torque, the output torque of the motor is close to the electromagnetic torque, and the stable reciprocating swing effect of the rotor assembly is achieved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of oral cleaning equipment, and in particular to a motor and an oral cleaning equipment. Background Art

[0002] Electric toothbrushes use motors to swing back and forth rapidly within a certain angle range, causing the brush head to produce high-frequency vibrations, which can effectively clean the teeth and mouth. Compared with traditional toothbrushes, they have improved cleaning abilities and are therefore favored by more and more consumers.

[0003] The motor of the existing oral cleaning device usually has a large cogging torque. The rotor needs to overcome the large cogging torque to achieve reciprocating swing, which greatly affects the performance of the motor. Summary of the invention

[0004] The purpose of the present disclosure is to overcome the deficiencies of the prior art and provide a motor and an oral cleaning device.

[0005] According to a first aspect of the present disclosure, a motor is provided for use in an oral cleaning device, the motor comprising: The rotor assembly comprises a rotor shaft extending along a rotation axis, and four magnets arranged on the rotor shaft in sequence and at equal intervals along a circumferential direction, wherein the magnetic properties of two adjacent magnets are opposite; A stator assembly, the stator assembly having four stator cores surrounding the rotor assembly and arranged in sequence at equal intervals in the circumferential direction, each of the stator cores being configured to mount a winding, and each of the windings being matched with two adjacent magnets; In at least one plane perpendicular to the rotation axis of the rotor assembly, with the intersection of the rotation axis and the plane as the center of the circle, the center angle of the outer arc segment of the magnet close to the stator core and the center angle of the inner arc segment of the stator core close to the magnet are both in the range of 71° to 81°.

[0006] In one embodiment of the present disclosure, the center angle of the outer arc segment of the magnet close to the stator core and the center angle of the inner arc segment of the stator core close to the magnet are both in the range of 74° to 78°.

[0007] In one embodiment of the present disclosure, the center angle of the outer arc segment of the magnet close to the stator core is equal to the center angle of the inner arc segment of the stator core close to the magnet.

[0008] In one embodiment of the present disclosure, the maximum single-sided swing angle of the rotor assembly ranges from 13° to 18.5°.

[0009] In one embodiment of the present disclosure, when the maximum value of the single-sided swing angle of the rotor assembly is in the range of 13° to 18.5°, the cogging torque of the motor is less than 5 mN*m.

[0010] In one embodiment of the present disclosure, when in a balanced position, two adjacent magnets correspond to two sides of the stator core, respectively, and the projections of the two adjacent magnets and the stator core along the radial direction with the point of the rotation axis as the projection center overlap: The overlap is equal; and / or, The central angle of the outer arc segment of the magnet close to the stator core in the overlapping part and the central angle of the inner arc segment of the stator core close to the magnet are both in the range of 26° to 36°.

[0011] In one embodiment of the present disclosure, a radial air gap is formed between an outer arc segment of the magnet close to the stator core and an inner arc segment of the stator core close to the magnet, and the width of the radial air gap remains equal along the circumferential direction.

[0012] In one embodiment of the present disclosure, the width of the radial air gap ranges from 0.1 mm to 0.3 mm.

[0013] In one embodiment of the present disclosure, the stator core comprises a circular ring fixing portion surrounding the rotor assembly, and the circular ring fixing portion is fixedly connected to the housing of the motor; The stator core includes a surrounding portion extending radially from the circular ring fixing portion, and the free end of the surrounding portion constitutes a partial arc segment of the inner arc segment, and two tooth portions extending circumferentially to the left and right sides from the free end of the surrounding portion, the two tooth portions forming another partial arc segment of the inner arc segment toward the magnet side, and the winding is wound on the surrounding portion.

[0014] In one embodiment of the present disclosure, the width of the surrounding portion ranges from 2.5 mm to 3.1 mm.

[0015] In one embodiment of the present disclosure, the annular fixing portion, the surrounding portion and the tooth portion are integrally formed.

[0016] In one embodiment of the present disclosure, in a plane perpendicular to the rotation axis of the rotor assembly, the cross-section of the surrounding portion includes two first straight line segments extending radially and parallel to each other, and the cross-section of the tooth portion includes a second straight line segment set at an angle to the first straight line segment, and a third straight line segment connecting the second straight line segment and the inner arc segment.

[0017] In one embodiment of the present disclosure, the angle formed by the first straight line segment and the second straight line segment ranges from 120° to 150°.

[0018] In one embodiment of the present disclosure, the stator assembly further includes: A first stator bobbin, the first stator bobbin is configured to be fixedly connected to the left end of the housing of the motor and has a first positioning collar matched with the shape of the spacing space between two adjacent stator cores, the first positioning collar being inserted into the spacing space from the left end; A second stator bobbin, the second stator bobbin is configured to be fixedly connected to the right end of the housing of the motor and has a second positioning collar matched with the shape of the spacing space between two adjacent stator cores, and the second positioning collar is inserted into the spacing space from the right end; The winding is wound around the surrounding portion through the first positioning collar and the second positioning collar; The rotor shaft rotatably penetrates the first stator bobbin and the second stator bobbin.

[0019] In one embodiment of the present disclosure, the rotor assembly further comprises a rotor core ring sleeved on the rotor shaft, the rotor core ring having a mounting groove, and the mounting groove is configured to fix the magnet.

[0020] In one embodiment of the present disclosure, in a plane perpendicular to the rotation axis of the rotor assembly, a ratio of a groove depth of the mounting groove to a thickness of the magnet is in a range of 0.3 to 0.5.

[0021] In one embodiment of the present disclosure, in a plane perpendicular to the rotation axis of the rotor assembly, the cross-sectional shape of the magnet is an arc shape, and the magnet includes an outer arc segment and an inner arc segment distributed in the radial direction, and two side edges respectively connecting the outer arc segment and the corresponding two ends of the inner arc segment; the central angles of the outer arc segment and the inner arc segment are the same.

[0022] In one embodiment of the present disclosure, the circumferential gap between two adjacent stator cores is larger than the circumferential gap between two adjacent magnets.

[0023] In one embodiment of the present disclosure, when the rotor shaft is driven by a torque component along the circumference of the rotation axis, the rotor shaft rotates in the direction of the torque component: If the torque component exceeds a preset value, the rotor shaft rotates to reach a next equilibrium position in the direction of the torque component.

[0024] In one embodiment of the present disclosure, the motor has four equilibrium positions.

[0025] In one embodiment of the present disclosure, in at least one plane perpendicular to the rotation axis of the rotor assembly, with the intersection of the rotation axis and the plane as the center of the circle, the angle between the first center line of the magnet in an equilibrium position and the second center line of the magnet in an adjacent equilibrium position is 90 degrees.

[0026] According to a second aspect of the present disclosure, an oral cleaning device is provided, comprising a main body and a motor disposed in the main body, wherein the motor is configured to drive a cleaning attachment to swing via a rotor assembly, and the motor is the motor described in any of the above embodiments.

[0027] One beneficial effect of the motor disclosed in the present invention is that, since the cogging torque is affected by the geometric structure of the stator assembly and the rotor assembly, different tooth shape designs will affect the amplitude of the cogging torque. Therefore, the motor provided by the present invention for oral cleaning equipment is a four-pole four-slot structure, the number of poles is equal to the number of slots, and the cogging torque corresponds to the change of the electromagnetic torque during the swing period of the rotor assembly. Since the output torque of the motor is the sum of the electromagnetic torque and the cogging torque, the output torque of the motor is basically positively correlated with the input current. On this basis, in at least one plane perpendicular to the rotation axis of the rotor assembly, with the intersection of the rotation axis and the plane as the center of the circle, the degree of the center angle of the outer arc segment of the selected magnet close to the stator core and the degree of the center angle of the inner arc segment of the selected magnet close to the magnet are both 71° to 81°. In the swing period of the rotor assembly, the constant torque interval is located in the area where the cogging torque is small, and the rotor assembly can achieve reciprocating swing without overcoming a large cogging torque. When the cogging torque is small, the output torque of the motor is close to the electromagnetic torque, so that in practice, the purpose of controlling the output torque can be achieved by controlling the input current.

[0028] It should be noted that the oral cleaning device of the present invention includes the above-mentioned motor and has the same technical effect as the motor of the present invention, which will not be repeated herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0030] Figure 1 is a schematic axial cross-sectional view of a motor provided in one embodiment of the present disclosure; Figure 2 is a radial cross-sectional schematic diagram of a motor provided in one embodiment of the present disclosure; Figure 3 is a schematic diagram of an exploded structure of a motor provided in one embodiment of the present disclosure; Figure 4is a schematic diagram of the position of a rotor assembly when a motor provided in an embodiment of the present disclosure is in a balanced position; Figure 5 is a schematic diagram of no-load magnetic flux distribution when the motor is in a balanced position in an electromagnetic simulation experiment provided in one embodiment of the present disclosure; Figure 6 It is a schematic diagram of no-load magnetic flux distribution when the rotor assembly is at the maximum unilateral swing angle position in the electromagnetic simulation experiment provided in one embodiment of the present disclosure; Figure 7 It is a data graph of three sets of electromagnetic simulation experiments provided in one embodiment of the present disclosure.

[0031] Figures 1 to 7 The one-to-one correspondence between the component names and the reference numerals is as follows: 1- rotor assembly; 11- rotor shaft; 12- magnet; 13- rotor core ring; 131- mounting groove; 2- stator assembly; 21- stator core; 211- annular fixing portion; 212- surrounding portion; 213- tooth portion; 22-winding; 23-first stator bobbin; 24-second stator bobbin; 3-housing; 4-transmission shaft; 5-end cover. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure unless otherwise specifically stated.

[0033] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0034] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0035] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0036] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0037] In this document, “upper”, “lower”, “front”, “back”, “left”, “right”, etc. are only used to indicate the relative position relationship between related parts, rather than to limit the absolute positions of these related parts.

[0038] In this article, "first", "second", etc. are only used to distinguish each other, and do not indicate the importance and order, or the premise of each other's existence.

[0039] In this document, “equal”, “same”, etc. are not strictly limited in a mathematical and / or geometric sense, but also include errors that can be understood by those skilled in the art and are allowed in manufacturing or use.

[0040] It should be noted that, in order to facilitate a better understanding of the technical solution of the present disclosure, the directional word setting rules and professional terms involved in the present disclosure are first explained.

[0041] In the present disclosure, axial direction refers to the direction along the rotation axis of the rotor shaft, circumferential direction refers to the circumferential direction around the rotation axis of the rotor shaft, and radial direction refers to the direction extending outward from the rotation center in a plane perpendicular to the rotation axis of the rotor shaft.

[0042] Cogging torque: Cogging torque is the torque generated by the interaction between the permanent magnet and the stator core when the permanent magnet motor winding is not energized. It is caused by the tangential component of the interaction force between the permanent magnet and the armature teeth.

[0043] Torque ripple: Torque ripple is the phenomenon that the output torque varies with time due to factors such as stator slotting and magnetic field harmonics.

[0044] Electromagnetic compatibility (EMC) refers to the ability of a device or system to operate in compliance with requirements in its electromagnetic environment and not produce intolerable electromagnetic interference to any device in its environment.

[0045] The motor used in the existing oral cleaning device has a large cogging torque, and the rotor needs to overcome a large cogging torque to achieve reciprocating swing. To this end, the present disclosure provides a motor.

[0046] The motor disclosed in the present invention comprises a rotor assembly and a stator assembly. The rotor assembly comprises a rotor shaft extending along a rotation axis, and four magnets arranged on the rotor shaft at equal intervals in a circumferential direction, and the magnetism of two adjacent magnets is opposite; the stator assembly comprises four stator cores surrounding the rotor assembly and arranged at equal intervals in a circumferential direction, each stator core is configured to install a winding, and each winding cooperates with two adjacent magnets; in at least one plane perpendicular to the rotation axis of the rotor assembly, with the intersection of the rotation axis and the plane as the center of the circle, the center angle of the outer arc segment of the magnet close to the stator core and the center angle of the inner arc segment of the stator core close to the magnet are both in the range of 71° to 81°.

[0047] In the motor with the four-pole four-slot structure disclosed in the present invention, since the number of poles is equal to the number of slots, the cogging torque corresponds to the change of the electromagnetic torque during the swing period of the rotor assembly. Since the output torque of the motor is the sum of the electromagnetic torque and the cogging torque, the output torque of the motor is basically positively correlated with the input current. On this basis, in at least one plane perpendicular to the rotation axis of the rotor assembly, with the intersection of the rotation axis and the plane as the center of the circle, the degree of the center angle of the outer arc segment of the magnet close to the stator core and the degree of the center angle of the inner arc segment of the stator core close to the magnet are both 71° to 81°. The constant torque interval is located in the area with smaller cogging torque during the swing period of the rotor assembly. The rotor assembly can also achieve reciprocating swing without overcoming a larger cogging torque. When the cogging torque is small, the output torque of the motor is close to the electromagnetic torque, so that in practice, the purpose of controlling the output torque can be achieved by controlling the input current, and the rotor assembly can achieve reciprocating swing without overcoming a larger cogging torque.

[0048] In addition, there are usually two types of motors used in existing oral cleaning devices. One type of motor uses open-loop control. When the motor is under load, the swing angle of the rotor decreases, and the swing amplitude of the cleaning attachment decreases accordingly, making it difficult to achieve a good cleaning effect, which greatly affects the user experience. The other type of motor uses hardware such as Hall sensors and control boards to achieve closed-loop control. Although it can keep the swing amplitude of the cleaning attachment unchanged under load pressure, the structure is complex. The motor disclosed in the present invention can achieve stable output torque control by controlling the input current, and then input a current of appropriate size to achieve more accurate swing control. The structure is very simple, reducing power consumption, cost and algorithm complexity. For example, by setting a simple pressure sensor to measure the load pressure, the swing amplitude of the cleaning attachment is kept unchanged under load pressure, such as controlling the output of vibration and / or sweeping with a larger swing angle to improve the cleaning effect.

[0049] For ease of understanding, refer to Figures 1 to 7 , the specific structure and working principle of the present invention are described in detail in combination with embodiments.

[0050] Reference Figures 1 to 3 The motor disclosed in the present invention is a concentrated winding limited angle torque motor with a four-pole four-slot structure. The rotor assembly 1 is provided with four magnets 12, and the stator assembly 2 is provided with four stator cores 21. A stator tooth slot is formed between each two adjacent stator cores 21. Therefore, the stator assembly 2 also includes four stator tooth slots that surround the rotor assembly 1 and are arranged in sequence at equal intervals in the circumferential direction. Since the number of poles is equal to the number of slots, there is only one tooth slot torque cycle in one electromagnetic torque cycle.

[0051] The winding 22 is a concentrated winding powered by a single-phase AC power supply, which can simplify the manufacturing process of the winding 22 compared to the distributed winding. The winding 22 also adopts a double-layer design, and the top and bottom of a stator tooth slot are provided with coil edges, so that the winding 22 can provide good magnetic field symmetry, optimize the magnetic flux distribution in the tooth slot, and reduce the influence of magnetic field harmonics. Each winding 22 cooperates with two adjacent magnets 12 with opposite magnetic properties to drive the rotor assembly 1 to rotate.

[0052] Since the cogging torque is affected by the geometric structures of the stator assembly 2 and the rotor assembly 1, different tooth profile designs will affect the amplitude of the cogging torque. Therefore, in at least one plane perpendicular to the rotation axis of the rotor assembly 1, with the intersection of the rotation axis and the plane as the center of the circle, the central angle of the outer arc segment of the magnet 12 close to the stator core 21 and the central angle of the inner arc segment of the stator core 21 close to the magnet 12 are both selected to be 71° to 81°, that is, Figure 1 The degree of the angle α inside.

[0053] The motor disclosed in the present invention further includes a housing 3, a transmission shaft 4 and an end cover 5. The housing 3 is cylindrical and is sleeved on the outside of the stator assembly 2 to accommodate the rotor assembly 1 and the stator assembly 2 of the motor. Two bearings are fixedly arranged on both sides of the housing 3 along the axial direction. The inner ring of the bearing is fixedly connected to the rotor shaft 11, and the rotor shaft 11 rotatably penetrates the housing 3. One end of the rotor shaft 11 passing through the housing 3 is coaxially fixedly connected to the transmission shaft 4. Under the rotation of the rotor shaft 11, the transmission shaft 4 drives the cleaning attachment to swing back and forth. The other end of the rotor shaft 11 passing through the housing 3 stops at the end cover 5, and the end cover 5 is fixedly connected to the housing 3.

[0054] Working principle: Reference Figure 4, when it is in the equilibrium position, the position of the rotor assembly 1 is taken as the 0° angle position, that is, the starting position, and the cogging torque is also 0 or close to 0. The rotor assembly 1 takes the 0° angle position as the starting point and deflects to one side by a certain angle θ, and this θ angle is the unilateral swing angle of the rotor assembly 1. When a positive current is applied to the motor, the electromagnetic torque drives the rotor assembly 1 to swing in the counterclockwise direction, and the cogging torque is opposite to the electromagnetic torque. In the swinging process of the rotor assembly 1, the cogging torque remains basically unchanged or gradually increases slightly. When the unilateral swing angle of the rotor assembly 1 is within the preset swing angle value, the cogging torque is basically 0. When the unilateral swing angle of the rotor assembly 1 exceeds the preset swing angle value, the cogging torque increases rapidly until the cogging torque is equal to the electromagnetic torque. At this time, the output torque is 0, and the unilateral swing angle of the rotor assembly 1 reaches the maximum value. When a reverse current is applied to the motor, the electromagnetic torque pushes the rotor assembly 1 to swing in the clockwise direction. After passing the 0° angle position, the cogging torque is opposite to the electromagnetic torque, which is the same as when the rotor assembly 1 swings counterclockwise. When the unilateral swing angle of the rotor assembly 1 is within the preset swing angle value, the cogging torque is basically 0. When the unilateral swing angle of the rotor assembly 1 exceeds the preset swing angle value, the cogging torque increases rapidly until the cogging torque is equal to the electromagnetic torque. At this time, the output torque is 0, and the unilateral swing angle of the rotor assembly 1 reaches the maximum value. After that, the above process is repeated. Among them, the preset swing angle value is the maximum unilateral swing angle. If the input current exceeds the preset current value, a larger electromagnetic torque can be input to overcome the cogging torque, so that the unilateral swing angle exceeds the preset swing angle value.

[0055] Within the preset swing angle value range, the motor has a fast response speed and can quickly reach the target swing angle position with precise control and quick response.

[0056] In one embodiment, the motor disclosed in the present invention has four equilibrium positions. Two adjacent magnets 12 form a magnet group, and a total of four magnet groups are formed along the circumferential direction of the rotation axis. Each magnet group forms a equilibrium position with four corresponding stator cores 21 and windings 22 installed thereon. When the rotor shaft 11 and the magnet group rotate circumferentially along the rotation axis, each magnet group reaches a position corresponding to the next stator core 21 and the windings 22 installed thereon in the rotation direction, and the position is the next equilibrium position. By analogy, when the rotor shaft 11 and the magnet group rotate 360 ​​degrees circumferentially along the rotation axis, each magnet group reaches four equilibrium positions cumulatively.

[0057] In one embodiment, in at least one plane perpendicular to the rotation axis of the rotor assembly 1, with the intersection of the rotation axis and the plane as the center of the circle, the angle between the first center line of the magnet 12 at a balanced position and the second center line of the magnet 12 at an adjacent balanced position is 90 degrees. In this embodiment, among the four balanced positions, the angle between any two adjacent balanced positions is 90 degrees. For example, in a plane perpendicular to the rotation axis of the rotor assembly 1, when the magnet 12 is at any balanced position, with the intersection of the rotation axis and the plane as the center of the circle, the current center line of the magnet 12 is determined as the first center line; when the magnet 12 is at a balanced position adjacent to the balanced position, the center line with the intersection of the rotation axis and the plane as the center of the circle is the second center line, then, the angle between the first center line and the second center line in the plane is 90 degrees.

[0058] Of course, as an implementation method, a line obtained by connecting any point of the magnet 12 in the plane with the center of the circle can be used as a reference line. Thus, the reference line when the magnet 12 is in any equilibrium position is the first reference line, and the reference line when the magnet 12 is in an equilibrium position adjacent to the equilibrium position is the second reference line. The angle between the first reference line and the second reference line is 90 degrees.

[0059] In one embodiment, when the rotor shaft 11 is driven by a torque component along the circumference of the rotation axis, the rotor shaft 11 rotates in the direction of the torque component: if the torque component exceeds a preset value, the rotor shaft 11 rotates to reach the next equilibrium position in the direction of the torque component.

[0060] The torque component may be a mechanical force applied externally to the rotor shaft 11, or an electromagnetic torque applied by the stator assembly 2. When the rotor shaft 11 is driven by an external force or current, the torque component along the axial direction of the rotation axis causes the rotor shaft 11 and the magnet 12 to rotate in the direction of the torque component until reaching a critical position with respect to the next adjacent equilibrium position. At the critical position, if the torque component exceeds a preset value, the rotor shaft and the magnet 12 can cross the critical position and reach the next equilibrium position in the direction of the torque component.

[0061] Thus, the user can manually adjust or adjust the balance position of the rotor shaft 11 and the magnet 12 by electric control, and then adjust the swing starting position of the rotor shaft 11. The cleaning attachment mounted on the rotor shaft 11 can also adjust the direction of the bristles accordingly, so that the user can adjust the direction of the cleaning attachment according to the needs. For example, the main surface of the main body of the oral cleaning device is equipped with a display device. For the convenience of observation, the user can adjust the balance position of the rotor shaft 11 and the magnet 12 so that the direction of the cleaning attachment is 180 degrees with the main surface. Therefore, when the user uses the oral cleaning device for oral cleaning, he can directly observe the various information displayed on the display device through a mirror, etc., so as to improve the cleaning efficiency. Of course, the balance position of the rotor shaft 11 and the magnet 12 can also be adjusted by inputting current, and then the direction of the cleaning attachment can be adjusted to achieve multi-angle cleaning. For example, the direction of the cleaning attachment is automatically adjusted according to the current posture, position and / or cleaning time of the oral cleaning device, so that the user does not need to manually adjust the posture of holding the oral cleaning device, and oral cleaning at multiple positions and angles can be achieved.

[0062] In one embodiment, the center angle of the outer arc segment of the magnet 12 close to the stator core 21 and the center angle of the inner arc segment of the stator core 21 close to the magnet 12 are both in the range of 74° to 78°.

[0063] Reference Figure 1 Preferably, after experimental measurement, when the center angle of the outer arc segment of the magnet 12 close to the stator core 21 and the center angle of the inner arc segment of the stator core 21 close to the magnet 12, that is, the angle α, are both in the range of 74° to 78°, the tooth torque in the constant torque range is smaller, and there is basically no effect on the output torque of the motor, thereby achieving stable operation of the motor.

[0064] In one embodiment, the center angle of the outer arc segment of the magnet 12 close to the stator core 21 is equal to the center angle of the inner arc segment of the stator core 21 close to the magnet 12 .

[0065] Specifically, refer to Figures 5 to 7 The magnetic field between the stator assembly 2 and the rotor assembly 1 is unevenly distributed, which affects the cogging torque. The center angle of the outer arc segment of the magnet 12 close to the stator core 21 is equal to the center angle of the inner arc segment of the stator core 21 close to the magnet 12. The magnetic flux distribution between the stator assembly 2 and the rotor assembly 1 can be optimized and the amplitude of the cogging torque can be reduced.

[0066] In one embodiment, the maximum value of the single-side swing angle of the rotor assembly 1 ranges from 13° to 18.5°, that is, the preset swing angle value ranges from 13° to 18.5°.

[0067] Specifically, refer to Figure 4Four groups of electromagnetic simulation experiments were conducted for the amplitude of the unilateral swing angle of the rotor assembly 1 in the constant torque area, respectively, in which no current, the first current value, the second current value, and the third current value were applied to the motor to obtain the electromagnetic torque at different positions of the rotor assembly 1, wherein the first current value, the second current value, and the third current value increase in sequence.

[0068] The first set of experiments: when no current is applied to the motor, the magnitude of the cogging torque at each position of the rotor assembly 1 within one cycle is obtained.

[0069] The second group of experiments: when the first current value is applied, the constant torque region is located in the swing angle range of the rotor assembly 1 from -18.5° to 18.5°, and the average torque size of the constant torque region is the first torque value.

[0070] The third group of experiments: when the second current value is applied, the constant torque region is located in the swing angle range of the rotor assembly 1 from -17° to 17°, and the average torque size of the constant torque region is the second torque value.

[0071] The fourth group of experiments: when the third current value is applied, the constant torque region is located in the swing angle range of the rotor assembly 1 from -13° to 13°, and the average torque size of the constant torque region is the third torque value.

[0072] Comparing the data of the second, third and fourth groups of experiments with the data of the first group of experiments, the constant torque area is located at a position where the cogging torque is close to 0. Therefore, when the maximum value of the single-sided swing angle of the rotor assembly 1 is 13° to 18.5°, the motor is little affected by the cogging torque, the output torque is basically equal to the electromagnetic torque, the operation of the motor remains stable, and the control is more precise.

[0073] In addition, a rule can be drawn from the second, third and fourth groups of experiments that as the applied current increases, the maximum value of the unilateral swing angle of the rotor assembly 1 in the constant torque area decreases, and the swing angle of the cleaning attachment of the oral cleaning device needs to reach -10° to 10°. If the swing angle is small, it is difficult to complete the cleaning work.

[0074] In one embodiment, when the maximum value of the single-sided swing angle of the rotor assembly 1 is in the range of 13° to 18.5°, the cogging torque of the motor is less than 5 mN*m.

[0075] Specifically, refer to Figure 4 , Figure 7When the maximum value of the single-side swing angle of the rotor assembly 1 is between 13° and 18.5°, the motor is in the constant torque region, and the magnitude of the electromagnetic torque is between the first torque value and the third torque value, and the first torque value and the third torque value are both much larger than 5mN*m. Within this range, the cogging torque of the motor is less than 5mN*m, and in most of the range, the cogging torque does not exceed 2mN*m. Therefore, within this range, the cogging torque has little effect on the electromagnetic torque.

[0076] In one embodiment, when in the equilibrium position, two adjacent magnets 12 correspond to the two sides of the stator core 21 respectively, and the projection parts of the two adjacent magnets 12 and the stator core 21 along the radial direction with the point of the rotation axis as the projection center overlap, and the overlapping parts are equal.

[0077] Specifically, refer to Figure 4 The equilibrium position is when the rotor assembly 1 is at an angle of 0°, at which point the cogging torque of the motor is 0. Two magnets 12 are symmetrically distributed on both sides of the axis of the stator core 21. By overlapping the projections of the magnets 12 and the stator core 21, the uneven torque caused by the interaction between the magnetic poles and the stator core 21 can be reduced to a certain extent, thereby reducing the noise and vibration of the motor during operation.

[0078] In another embodiment, when in the equilibrium position, two adjacent magnets 12 correspond to the two sides of the stator core 21, and the projections of the two adjacent magnets 12 and the stator core 21 along the radial direction with the point of the rotation axis as the projection center overlap, and the overlapping parts are equal. And / or the center angle of the outer arc segment of the magnet 12 close to the stator core 21 in the overlapping part and the center angle of the inner arc segment of the stator core 21 close to the magnet 12 are both in the range of 26° to 36°.

[0079] When the center angle of the outer arc segment of the overlapping part of the magnet 12 close to the stator core 21 and the center angle of the inner arc segment of the stator core 21 close to the magnet 12 are both in the range of 26° to 36°, the magnetic field distribution inside the motor can be optimized, making the motor more stable and efficient during operation. In one embodiment, a radial air gap is formed between an outer arc segment of the magnet 12 close to the stator core 21 and an inner arc segment of the stator core 21 close to the magnet 12 , and the width of the radial air gap remains the same along the circumferential direction.

[0080] Specifically, the radial air gap has a significant effect on the torque. The width of the radial air gap is the distance between the magnet 12 and the stator core 21. When the width of the radial air gap is changed, the magnetic flux of the rotor assembly 1 through the coil of the winding 22 changes accordingly. If the radial air gap is not uniform, the variation law of the cogging torque will change within a cycle. Therefore, in order to ensure uniform distribution of the magnetic field and smooth operation of the motor, it is necessary to strictly control the uniformity of the radial air gap so that the distance between the magnet 12 and the stator core 21 is kept equal at each point in the circumferential direction.

[0081] In one embodiment, the width of the radial air gap ranges from 0.1 mm to 0.3 mm.

[0082] Specifically, the width of the radial air gap affects the magnetic circuit characteristics of the motor, thereby affecting the cogging torque of the motor. When the width of the radial air gap increases, due to the increase in the length of the magnetic circuit between the stator assembly 2 and the rotor assembly 1, the magnetic resistance of the motor will also increase, resulting in a decrease in the cogging torque of the motor. The width of the radial air gap will also affect the electromagnetic induction characteristics of the motor, thereby affecting the cogging torque of the motor. When the width of the radial air gap increases, due to the decrease in the magnetic flux density of the rotor assembly 1, the magnetic field strength of the motor will also decrease, resulting in a decrease in the cogging torque of the motor. Therefore, increasing the width of the radial air gap can effectively reduce the cogging torque.

[0083] However, increasing the width of the radial air gap will reduce the efficiency and maximum torque of the motor, so it is necessary to reasonably select the width range of the radial air gap. Preferably, the motor disclosed herein uses a radial air gap with a width range of 0.1 mm to 0.3 mm, which achieves the purpose of reducing the motor cogging torque while ensuring that the efficiency and maximum torque of the motor meet the working requirements.

[0084] In one embodiment, the stator core 21 includes a circular ring fixing portion 211 surrounding the rotor assembly 1, and the circular ring fixing portion 211 is fixedly connected to the housing 3 of the motor; the stator core 21 includes a surrounding portion 212 extending radially from the circular ring fixing portion 211, and the free end of the surrounding portion 212 constitutes a partial arc segment of the inner arc segment, and two tooth portions 213 extending circumferentially from the free end of the surrounding portion 212 to the left and right sides, and the two tooth portions 213 form another partial arc segment of the inner arc segment toward the side of the magnet 12, and the winding 22 is wound on the surrounding portion 212.

[0085] Specifically, the annular fixing portion 211 serves as the outer annular portion of the stator core 21 , and is mainly used to fix the entire stator assembly 2 structure, provide sufficient mechanical strength to support other components on the stator assembly 2 , and is installed in the motor housing 3 through the annular fixing portion 211 .

[0086] The surrounding portion 212 is the middle part of the stator core 21, which is formed by the circular fixing portion 211 extending radially inward and surrounds the rotor shaft 11 of the motor. The winding 22 is wound on the surrounding portion 212. The free end of the surrounding portion 212 is a part of the inner arc segment, which interacts with two adjacent magnets 12 to drive the rotor assembly 1 to swing back and forth.

[0087] The free end of each surrounding portion 212 extends two teeth 213 circumferentially to the left and right sides, and the two teeth 213 and the free end of the surrounding portion 212 form a complete inner arc segment, and the radial projection length of the inner arc segment is greater than the width of the surrounding portion 212, so that the winding 22 is clamped on the surrounding portion 212 to prevent the winding 22 from falling off the surrounding portion 212.

[0088] In one embodiment, the width of the surrounding portion 212 ranges from 2.5 mm to 3.1 mm.

[0089] Specifically, the surrounding portion 212 is a component for winding the winding 22 in the stator assembly 2, so the width of the surrounding portion 212 determines the magnetic flux and magnetic flux density of the stator assembly 2. In addition, the width of the surrounding portion 212 will also affect the cogging effect. Increasing the width of the surrounding portion 212 can carry more magnetic flux, reduce the magnetic flux density, and improve the efficiency and output torque of the motor. At the same time, the wider surrounding portion 212 can increase the larger surface area, which is conducive to heat dissipation and improves the performance and service life of the motor. However, the uneven torque generated by the interaction between the surrounding portion 212 and the magnet 12 increases the cogging torque. Therefore, it is necessary to compromise and select a reasonable width range of the surrounding portion 212. Preferably, the width range of the surrounding portion 212 of the motor disclosed in the present invention is 2.5mm to 3.1mm.

[0090] In one embodiment, the annular fixing portion 211 , the surrounding portion 212 and the tooth portion 213 are integrally formed.

[0091] Specifically, one-piece molding can avoid weak links caused by welding or assembly, thereby improving the mechanical strength of the entire stator assembly 2 structure, reducing the manufacturing and subsequent assembly process of multiple components, simplifying the manufacturing process, reducing manufacturing difficulty and cost, and is suitable for automated production lines, which can improve production efficiency and reduce labor costs.

[0092] During the one-piece molding process, the relative positions of the various components can be better controlled, especially the positional relationship between the surrounding portion 212 and the tooth portion 213, which directly affects the curvature of the inner arc segment, and then indirectly affects the width of the radial air gap between the stator assembly 2 and the rotor assembly 1 and whether the radial air gap is uniform along the circumferential direction. Through one-piece molding, the curvature of the surrounding portion 212 and the tooth portion 213 is consistent, the radial air gap is kept uniform in the circumferential direction, the magnetic field is evenly distributed, and the cogging torque of the motor is reduced.

[0093] In one embodiment, in a plane perpendicular to the rotation axis of the rotor assembly 1, the cross-section of the surrounding portion 212 includes two first straight line segments extending radially and parallel to each other, and the cross-section of the tooth portion 213 includes a second straight line segment set at an angle to the first straight line segment, and a third straight line segment connecting the second straight line segment and the inner arc segment.

[0094] Specifically, two mutually parallel first straight line segments constitute the basic frame of the surrounding portion 212, so that the magnetic flux can pass through evenly. The distance between the two first straight line segments is the width of the surrounding portion 212. By setting the width of the surrounding portion 212, the cogging torque of the motor can be reduced and the efficiency and output torque of the motor can be improved.

[0095] The second straight line segment is arranged at a certain angle to the first straight line segment of the surrounding portion 212. This inclined design helps to optimize the magnetic field distribution, reduce the cogging effect, and improve the running stability of the motor.

[0096] The third straight line segment plays a transition role, connecting the inclined portion and the inner arc segment of the tooth portion 213 to form a complete cross section of the tooth portion 213 .

[0097] In one embodiment, the angle formed by the first straight line segment and the second straight line segment ranges from 120° to 150°.

[0098] Specifically, the first straight line segment and the second straight line segment are arranged obliquely to achieve an effect similar to a curved surface. Compared with the vertical arrangement of the first straight line segment and the second straight line segment, the thickness of the tooth portion 213 is more uniform, which optimizes the distribution of the magnetic field. Compared with the arrangement of the curved line segment, the processing process is simplified.

[0099] In one embodiment, the stator assembly 2 further includes a first stator bobbin 23 and a second stator bobbin 24. The first stator bobbin 23 is configured to be fixedly connected to the left end of the motor housing 3, and has a first positioning collar adapted to the shape of the spacing space between two adjacent stator cores 21, and the first positioning collar is inserted into the spacing space from the left end; the second stator bobbin 24 is configured to be fixedly connected to the right end of the motor housing 3, and has a second positioning collar adapted to the shape of the spacing space between two adjacent stator cores 21, and the second positioning collar is inserted into the spacing space from the right end; the winding 22 is wound around the surrounding portion 212 through the first positioning collar and the second positioning collar; the rotor shaft 11 rotatably passes through the first stator bobbin 23 and the second stator bobbin 24.

[0100] Specifically, the first stator bobbin 23 and the second stator bobbin 24 are provided with positioning end faces perpendicular to the axial direction of the rotor shaft 11, one side of the positioning end faces is fixedly connected to the housing 3 of the motor, and the other side is protrudingly provided with a first positioning collar and a second positioning collar that are adapted to the shape of the spacing space between two adjacent stator cores 21, and the first positioning collar and the second positioning collar are inserted into the stator core 21 through the spacing space between two adjacent stator cores 21 until both sides of the stator core 21 abut against the positioning end faces, and the winding 22 is wound on the contact surface between the first positioning collar, the second positioning collar and the surrounding portion 212. The rotor shaft 11 passes through the first stator bobbin 23 and the second stator bobbin 24, and is matched and connected with the bearing on the motor housing 3. By providing the first stator bobbin 23 and the second stator bobbin 24 on both sides of the stator core 21, the stator core 21 is fixed to the motor housing 3.

[0101] In one embodiment, the rotor assembly 1 further includes a rotor core ring 13 sleeved on the rotor shaft 11 . The rotor core ring 13 has a mounting groove 131 . The mounting groove 131 is configured to fix the magnet 12 .

[0102] Specifically, the inner diameter of the rotor core ring 13 is equal to the diameter of the rotor shaft 11, and is fixed to the rotor shaft 11 by adhesive or interference fit. Four mounting grooves 131 are arranged at equal intervals along the circumference, and the cross-sectional shape of the mounting groove 131 perpendicular to the axial direction of the rotor shaft 11 is adapted to the cross-sectional shape of the magnet 12 perpendicular to the axial direction of the rotor shaft 11, and the magnet 12 is embedded in the mounting groove 131 by adhesive or interference fit. By setting the mounting groove 131, the magnet 12 is firmly set on the rotor core ring 13 and rotates smoothly with the rotor shaft 11. Since adjacent magnets 12 are permanent magnets with opposite magnetic properties, setting the mounting groove 131 can also reduce the influence between the magnets 12.

[0103] In one embodiment, in a plane perpendicular to the rotation axis of the rotor assembly 1 , a ratio of a groove depth of the mounting groove 131 to a thickness of the magnet 12 is in a range of 0.3 to 0.5.

[0104] Specifically, the depth of the mounting groove 131 will affect the distribution of the magnetic field. A groove depth that is too shallow may result in the magnet 12 not being fully utilized, thereby reducing the efficiency of the motor. The magnet 12 may also not be firmly fixed in the mounting groove 131, and may easily be displaced or even fall off when the motor rotates at high speed. A groove depth that is too deep may increase unnecessary material usage, and although it can better fix the magnet 12, it will increase the stress of the magnet 12.

[0105] The motor disclosed herein selects a ratio of the slot depth to the thickness of the magnet 12 in the range of 0.3 to 0.5, which can help optimize the magnetic field distribution, reduce magnetic flux leakage, and improve the efficiency of the motor.

[0106] In one embodiment, in a plane perpendicular to the rotation axis of the rotor assembly 1, the cross-sectional shape of the magnet 12 is an arc shape, and the magnet 12 includes an outer arc segment and an inner arc segment distributed in the radial direction, and two side edges respectively connecting the corresponding two ends of the outer arc segment and the inner arc segment; the central angles of the outer arc segment and the inner arc segment are the same.

[0107] Specifically, the magnet 12 needs to be embedded and fixed with the mounting groove 131 on the rotor core ring 13. Since the mounting surface of the mounting groove 131 and the magnet 12 is arc-shaped, the cross-sectional shape of the magnet 12 is correspondingly arc-shaped, which is adapted to the mounting surface of the mounting groove 131, and the curvature of the mounting surface of the inner arc segment and the outer arc segment is consistent with that of the mounting surface of the mounting groove 131. The two sides connect the two ends of the outer arc segment and the inner arc segment to form a closed cross-sectional shape, which ensures that the magnet 12 has a stable structure in the radial direction and also helps to fix the magnet 12. The angles of the central angles corresponding to the outer arc segment and the inner arc segment are the same, that is, the magnet 12 presents a symmetrical shape in the radial direction. This design can ensure that the magnetic field strength of the magnet 12 at different radial positions is consistent, thereby reducing the non-uniformity of the magnetic field, and the transfer of magnetic flux between the rotor and the stator is more uniform, thereby reducing the cogging effect.

[0108] In one embodiment, the circumferential gap between two adjacent stator cores 21 is larger than the circumferential gap between two adjacent magnets 12 .

[0109] Specifically, the stator core 21 is arranged on the outside of the magnet 12, and the circumferential gap between two adjacent stator cores 21, that is, the width of the tooth slot in the stator assembly 2, when the tooth slot width is increased, the mutual influence of the magnetic field between adjacent teeth 213 is reduced. In this way, the magnetic field around the entire stator assembly 2 can be made more uniform, thereby reducing the cogging effect caused by the uneven magnetic field between adjacent teeth 213. Since the cogging effect will cause electromagnetic interference to the harmonic components generated by the motor, increasing the tooth slot width also helps to improve the electromagnetic compatibility of the motor.

[0110] The reduction in the circumferential gap between two adjacent magnets 12 can make the magnetic field of the rotor assembly 1 more concentrated, thereby enhancing the output torque of the motor.

[0111] In addition to the above-mentioned motor used in the oral cleaning device, the present disclosure also provides an oral cleaning device, which includes a main body and a motor arranged in the main body. The motor is configured to drive the cleaning attachment to swing through the rotor assembly 1. The motor is the motor described in any of the above-mentioned embodiments.

[0112] In one embodiment, the oral cleaning device includes an electric toothbrush, an electric water flosser, a tongue cleaner and other devices. The motor disclosed in the present invention can enable the oral cleaning device to achieve a stable output torque under load, so that the cleaning attachment maintains a constant swing amplitude under load pressure, thereby improving the user experience.

[0113] The oral cleaning device disclosed in the present invention is also provided with a pressure sensor for detecting the load pressure of the cleaning attachment. The relationship between the current and the output torque is obtained through simulation experiments to control the input of the motor current, thereby achieving a constant swing amplitude of the cleaning attachment and a simple structure.

[0114] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the marketplace, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein. The scope of the present disclosure is defined by the appended claims.

Claims

1. A motor, used in an oral cleaning device, characterized in that: The motor comprises: A rotor assembly (1) comprising a rotor shaft (11) extending along a rotation axis, and four magnets (12) arranged on the rotor shaft (11) in sequence and at equal intervals in a circumferential direction, wherein two adjacent magnets (12) have opposite magnetic properties; A stator assembly (2), the stator assembly (2) comprising four stator cores (21) surrounding the rotor assembly (1) and arranged in sequence at equal intervals in a circumferential direction, each of the stator cores (21) being configured to mount a winding (22), each of the windings (22) cooperating with two adjacent magnets (12); In at least one plane perpendicular to the rotation axis of the rotor assembly (1), with the intersection of the rotation axis and the plane as the center of the circle, the center angle of the outer arc segment of the magnet (12) close to the stator core (21) and the center angle of the inner arc segment of the stator core (21) close to the magnet (12) are both in the range of 71° to 81°.

2. The motor according to claim 1, characterized in that The center angle of the outer arc segment of the magnet (12) close to the stator core (21) and the center angle of the inner arc segment of the stator core (21) close to the magnet (12) are both in the range of 74° to 78°.

3. The motor according to claim 1 or 2, characterized in that: The center angle of the outer arc segment of the magnet (12) close to the stator core (21) is equal to the center angle of the inner arc segment of the stator core (21) close to the magnet (12).

4. The motor according to claim 3, characterized in that The maximum value of the single-sided swing angle of the rotor assembly (1) ranges from 13° to 18.5°.

5. The motor according to claim 4, characterized in that When the maximum value of the single-sided swing angle of the rotor assembly (1) is in the range of 13° to 18.5°, the cogging torque of the motor is less than 5 mN*m.

6. The motor according to claim 5, characterized in that When in a balanced position, two adjacent magnets (12) correspond to two sides of the stator core (21), respectively, and the projections of the two adjacent magnets (12) and the stator core (21) in a radial direction with the point of the rotation axis as the projection center overlap: The overlap is equal; and / or, The center angle of the outer arc section of the magnet (12) close to the stator core (21) in the overlapping portion and the center angle of the inner arc section of the stator core (21) close to the magnet (12) are both in the range of 26° to 36°.

7. The motor according to claim 6, characterized in that A radial air gap is formed between an outer arc section of the magnet (12) close to the stator core (21) and an inner arc section of the stator core (21) close to the magnet (12), and the width of the radial air gap remains equal along the circumferential direction.

8. The motor according to claim 7, characterized in that The width of the radial air gap ranges from 0.1 mm to 0.3 mm.

9. The motor according to claim 8, characterized in that The stator core (21) comprises a circular ring fixing portion (211) surrounding the rotor assembly (1), and the circular ring fixing portion (211) is fixedly connected to the housing of the motor; The stator core (21) comprises a surrounding portion (212) extending radially from the annular fixing portion (211), the free end of the surrounding portion (212) constituting a partial arc segment of the inner arc segment, and two tooth portions (213) extending circumferentially from the free end of the surrounding portion (212) to the left and right sides, the two tooth portions (213) forming another partial arc segment of the inner arc segment towards the side of the magnet (12), and the winding (22) is wound on the surrounding portion (212).

10. The motor according to claim 9, characterized in that The width of the surrounding portion (212) ranges from 2.5 mm to 3.1 mm.

11. The motor according to claim 9, characterized in that The annular fixing portion (211), the surrounding portion (212) and the tooth portion (213) are integrally formed.

12. The motor according to claim 11, characterized in that In a plane perpendicular to the rotation axis of the rotor assembly (1), a cross section of the surrounding portion (212) comprises two first straight line segments extending radially and parallel to each other, and a cross section of the tooth portion (213) comprises a second straight line segment arranged at an angle to the first straight line segment, and a third straight line segment connecting the second straight line segment and the inner arc segment.

13. The motor according to claim 12, characterized in that The angle formed by the first straight line segment and the second straight line segment ranges from 120° to 150°.

14. The motor according to claim 9, characterized in that The stator assembly (2) further comprises: A first stator bobbin (23), the first stator bobbin (23) being configured to be fixedly connected to the left end of the housing of the motor and having a first positioning collar matched to the shape of the spacing space between two adjacent stator cores (21), the first positioning collar being inserted into the spacing space from the left end; A second stator bobbin (24), the second stator bobbin (24) being configured to be fixedly connected to the right end of the housing of the motor and having a second positioning collar matched to the shape of the spacing space between two adjacent stator cores (21), the second positioning collar being inserted into the spacing space from the right end; The winding (22) is wound around the surrounding portion (212) through the first positioning collar and the second positioning collar; The rotor shaft (11) rotatably penetrates the first stator bobbin (23) and the second stator bobbin (24).

15. The motor according to claim 1, characterized in that The rotor assembly (1) further comprises a rotor core ring (13) sleeved on the rotor shaft (11), the rotor core ring (13) having a mounting groove (131), and the mounting groove (131) is configured to fix the magnet (12).

16. The motor according to claim 12, characterized in that In a plane perpendicular to the rotation axis of the rotor assembly (1), the ratio of the groove depth of the mounting groove (131) to the thickness of the magnet (12) is in the range of 0.3 to 0.

5.

17. The motor according to claim 1, characterized in that In a plane perpendicular to the rotation axis of the rotor assembly (1), the cross-sectional shape of the magnet (12) is in the shape of an arc, and the magnet (12) comprises an outer arc segment and an inner arc segment distributed in a radial direction, and two side edges respectively connecting the outer arc segment and the inner arc segment at two corresponding ends; the central angles of the outer arc segment and the inner arc segment are the same.

18. The motor according to claim 1, characterized in that The circumferential gap between two adjacent stator cores (21) is larger than the circumferential gap between two adjacent magnets (12).

19. The motor according to claim 1, characterized in that When the rotor shaft (11) is driven by a torque component along the circumference of the rotation axis, the rotor shaft (11) rotates in the direction of the torque component: If the torque component exceeds a preset value, the rotor shaft (11) rotates to reach the next equilibrium position in the direction of the torque component.

20. The electric machine according to claim 1, characterized in that The motor has four equilibrium positions.

21. The electric machine according to claim 20, characterized in that In at least one plane perpendicular to the rotation axis of the rotor assembly (1), with the intersection of the rotation axis and the plane as the center of the circle, the angle between a first center line of the magnet (12) at an equilibrium position and a second center line of the magnet (12) at an adjacent equilibrium position is 90 degrees.

22. An oral cleaning device, comprising a main body and a motor disposed in the main body, wherein the motor is configured to drive a cleaning attachment to swing through a rotor assembly (1), characterized in that: The motor is the motor according to any one of claims 1 to 21.

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