A method for positioning the flat angle of a motor's rotating shaft using cogging torque

Abstract

The present invention relates to the field of motor technology, and in particular to a method for positioning the flat angle of a motor rotating shaft by using cogging torque, comprising the following steps: designing and manufacturing a die head with a positioning function; fitting a stator core and the die head to position the stator core; fitting a housing and the die head to position the angle of the housing and the stator core after assembly; fixing the flat angle of the motor rotating shaft in a rotor structure to face the center of a magnetic pole; assembling all assembled motor components into a finished motor; after the motor is assembled, rotating the motor rotating shaft one circle with the winding not energized, and locking the flat angle of the motor rotating shaft at 12 positions, namely, 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°. Compared with the existing technology, the method of using the cogging torque to locate the angle of the motor's rotating shaft in the present invention can realize that when the motor winding is not powered, the motor's own positioning torque, namely the cogging torque, is used to lock the position of the rotating shaft, so that the motor's rotating shaft can be fixed at several specified positions according to the design requirements, meeting the product design requirements, reducing the complexity of the structure and the difficulty of the software control algorithm, achieving cost reduction and efficiency improvement, and improving the product's market competitiveness.

Description

Technical field

[0001] The present invention relates to the technical field of motors, and in particular to a method for positioning the flat angle of a motor rotating shaft by utilizing cogging torque. [Background Technology]

[0002] When the permanent magnets in a permanent magnet motor are deenergized, the interaction between the permanent magnets and the iron core creates a detent torque, also known as cogging torque. Cogging torque is caused by fluctuations in the tangential component of the interaction force between the permanent magnets and the armature teeth. When the rotor permanent magnets meet or separate from the stator teeth, the magnetic fields surrounding them change, causing a change in the magnetic energy of the air between the permanent magnets and the stator teeth. This change in magnetic energy generates torque, known as detent torque or cogging torque.

[0003] Therefore, when the permanent magnet motor winding is not energized, the motor rotating shaft will randomly lock in certain positions under the influence of the slot torque, affecting the use of the product.

[0004] For example, for an electric toothbrush, the position of the bristles (the flat position of the motor shaft) needs to correspond to the position of the handle button, that is, the direction of the bristles (the flat position of the shaft) and the handle button must be consistent, and the positional relationship between the bristles (the flat position of the motor shaft) and the handle button (motor installation position) must be accurately located.

[0005] Existing brush head positioning solutions fall into two main categories: 1. Mechanically locking the brush head when power is off and disengaging the locking mechanism when power is on. This approach is complex, costly, and noisy. 2. Reducing cogging torque relies on driver software control algorithms and motor brakes to lock the brush head. These algorithms are complex and challenging, and the product requires constant power on, resulting in high energy consumption, short charging cycles, and a shortened battery life. [Summary of the invention]

[0006] In order to overcome the above problems, the present invention proposes a method for positioning the flat angle of the motor rotating shaft using the cogging torque, which can effectively solve the above problems.

[0007] The present invention provides a technical solution to solve the above technical problems: providing a method for positioning the flat angle of the motor rotating shaft using the cogging torque, comprising the following steps:

[0008] Step S1, designing and manufacturing a die head with a positioning function;

[0009] Step S2, installing the stator core and the die head together and positioning the stator core;

[0010] Step S3, assembling the housing and the die head, and positioning the angle of the housing and the stator core after assembly;

[0011] Step S4, the motor rotating shaft in the rotor structure is fixed so that the flat part is aligned with the center of the magnetic pole;

[0012] Step S5, assembling all assembled motor components into a finished motor;

[0013] Step S6, after the motor is assembled, rotate the motor shaft one circle when the winding is not powered, and the motor shaft is locked at 12 positions of 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330° respectively.

[0014] Preferably, in step S1, a first key and a second key are provided on the die head, and the first key and the second key are distributed at an X angle, where the X angle is the angle between the center line of the stator slot and the center line of the stator tooth.

[0015] Preferably, the number of the first keys is less than or equal to the number of stator slots in the stator core, and the first keys are evenly distributed on the die head.

[0016] Preferably, in step S2, the first key is inserted into the stator tooth slot in the stator core to position the stator core.

[0017] Preferably, in step S3, a positioning notch or other characteristic portion with a positioning function matching the second key is provided on the casing, the positioning notch or other characteristic portion with a positioning function is assembled with the second key, and then the stator core and the casing are fixed by gluing.

[0018] Preferably, a housing mounting hole is provided on the housing, and the housing mounting hole corresponds to the positioning notch.

[0019] Preferably, the center line of the positioning notch coincides with the center line of the stator teeth.

[0020] Preferably, in step S4, the motor rotating shaft is fixed opposite the magnetic pole center in one way: the rotor core itself has a positioning keyway structure, the motor rotating shaft keyway faces the positioning keyway structure of the rotor core, and the angle is fixed by the positioning key.

[0021] Preferably, in step S4, there is a second method for fixing the flat part of the motor rotating shaft to face the center of the magnetic pole. The rotor core does not have a positioning keyway structure, and a jig is designed to locate the flat part of the rotor core and the motor rotating shaft. The rotor core and the motor rotating shaft are respectively installed in the jig, and the motor rotating shaft and the rotor core can be fixed by glue or interference fit.

[0022] Preferably, the flat position of the motor rotating shaft is aligned with the N pole or S pole position of the magnetic steel.

[0023] Compared with the existing technology, the method of using the cogging torque to locate the angle of the motor's rotating shaft in the present invention can realize that when the motor winding is not powered, the motor's own positioning torque, namely the cogging torque, is used to lock the position of the rotating shaft, so that the motor's rotating shaft can be fixed at several specified positions according to the design requirements, meeting the product design requirements, reducing the complexity of the structure and the difficulty of the software control algorithm, achieving cost reduction and efficiency improvement, and improving the product's market competitiveness.

Brief Description of the Drawings

[0024] Figure 1 A three-dimensional diagram of a die head for positioning the flat angle of a motor rotating shaft using cogging torque according to the present invention;

[0025] Figure 2 This is an axial view of the die head of the method for positioning the flat angle of the motor rotating shaft using the cogging torque of the present invention;

[0026] Figure 3 This is a stereoscopic diagram of the assembly of the stator core and the die head in the method of positioning the flat angle of the motor rotating shaft by using the cogging torque of the present invention;

[0027] Figure 4 This is an axial view of the assembly of the stator core and the die head in the method of positioning the flat angle of the motor rotating shaft by using the cogging torque of the present invention;

[0028] Figure 5 A perspective view of the assembly of a housing and a die head for the method of positioning the flat angle of a motor rotating shaft using cogging torque according to the present invention;

[0029] Figure 6 This is an axial view of the assembly of the housing and the die head of the method for positioning the flat angle of the motor rotating shaft by using the cogging torque of the present invention;

[0030] Figure 7 Schematic diagram of the assembly of the motor rotating shaft and the magnetic steel in the method of positioning the flat angle of the motor rotating shaft by using the cogging torque of the present invention;

[0031] Figure 8 Schematic diagram of the unstable equilibrium point of the method for positioning the flat angle of the motor rotating shaft using the cogging torque of the present invention;

[0032] Figure 9 This is a schematic diagram of a first stable equilibrium state of the method for positioning the flat angle of the motor rotating shaft using the cogging torque of the present invention;

[0033] Figure 10 Schematic diagram of the second stable equilibrium state of the method for positioning the flat angle of the motor rotating shaft by using the cogging torque of the present invention;

[0034] Figure 11 This is a cross-sectional view of the motor structure of the method of the present invention for positioning the flat angle of the motor rotating shaft using the cogging torque. [Specific implementation method]

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] It should be noted that in the embodiment of the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are limited to relative positions on the specified view, rather than absolute positions.

[0037] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referenced. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0038] See also Figures 1 to 11 The method of positioning the angle of the motor shaft using the cogging torque of the present invention specifically relates to a design method for positioning the motor shaft angle at several specified positions by rotating the motor shaft when the motor winding is not energized, including the following steps:

[0039] Step S1: designing and manufacturing a die head 100 with a positioning function.

[0040] In step S1 , the die head 100 is provided with a first key 110 and a second key 120 , which are distributed at an X angle. The X angle is the angle between the center line of the stator slot 51 and the center line a of the stator tooth, and is determined by the stator core 5 .

[0041] The number of the first keys 110 is less than or equal to the number of the stator slots 51 in the stator core 5 , and the first keys 110 are evenly distributed on the die head 100 .

[0042] Step S2 , the stator core 5 is assembled with the die head 100 and the stator core 5 is positioned.

[0043] In step S2 , the first key 110 is inserted into the stator slot 51 in the stator core 5 to position the stator core 5 .

[0044] Step S3 , the housing 9 and the die head 100 are assembled together, and the angle between the housing 9 and the stator core 5 after assembly is positioned.

[0045] In step S3, the housing 9 is provided with a positioning notch 91 or other feature having a positioning function that matches the second key 120. The positioning notch or other feature having a positioning function is assembled with the second key 120, and then the stator core 5 and the housing 9 are fixed with glue. The housing 9 is provided with a housing mounting hole 92, which corresponds to the positioning notch 91.

[0046] The center line b of the positioning notch 91 coincides with the center line a of the stator teeth.

[0047] Step S4: the motor rotating shaft 8 in the rotor structure is fixed so that the flat position is aligned with the center of the magnetic pole.

[0048] In step S4, there are two ways to fix the motor rotating shaft 8 in a straight line with the magnetic pole center:

[0049] Method 1: The rotor core 7 itself has a positioning keyway structure, and the keyway of the motor rotating shaft 8 is aligned with the positioning keyway structure of the rotor core 7, and the angle is fixed by the positioning key;

[0050] Method 2: The rotor core 7 does not have a positioning keyway structure, and a jig is needed to design to locate the flat position of the rotor core 7 and the motor rotating shaft 8. The rotor core 7 and the motor rotating shaft 8 are respectively installed in the jig, and the motor rotating shaft 8 and the rotor core 7 can be fixed by glue or interference fit.

[0051] The flat position of the motor rotating shaft 8 is aligned with the N pole or S pole position of the magnetic steel 6.

[0052] Step S5: assemble all assembled motor components into a finished motor.

[0053] Step S6, after the motor is assembled, the motor shaft 8 is rotated one circle without power to the winding, and the motor shaft 8 is locked at 12 positions of 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, 330°, and 360° (0°).

[0054] The present invention utilizes cogging torque to position the angle of the motor's rotating shaft. This method utilizes the permanent magnet motor's inherent positioning torque (cogging torque) to ensure that the stable equilibrium point of the cogging torque, i.e., the shaft's flattening angle, is aligned with the housing mounting hole or positioning notch. The center of a stator core 5 tooth aligns with the mounting hole or positioning notch in the motor housing 9, and the center of the rotor assembly's magnet 6 aligns with the motor's rotating shaft 8 flattening angle. After the motor is assembled, rotating the motor's rotating shaft 8 locks the flattening angle of the motor shaft 8 at the position where the stator teeth and magnets align, i.e., the motor's rotating shaft 8 flattening angle is aligned with the motor mounting hole, thereby locking the motor's rotating shaft 8 flattening angle in the designated position.

[0055] The method of the present invention for positioning the flat angle of the motor rotating shaft by using the cogging torque is a design method that utilizes the cogging torque of the permanent magnet motor itself and realizes locking the rotating shaft at a specified position through a specific combination of motor parts such as the stator, rotor and housing.

[0056] See also Figures 8 to 10 The principle of the method for positioning the flat angle of the motor rotating shaft by using the cogging torque of the present invention is as follows:

[0057] When the winding is not powered, the motor has six stator teeth and the rotor is equipped with four permanent magnets with N and N poles arranged in sequence, in any position. When the rotor rotates counterclockwise, when the relative position of the rotors is 45° (i.e., θ = 45), the resultant rotor torque is zero. This position is called the equilibrium point.

[0058] Since the rotor always tends to move to a position with smaller magnetic resistance and will not stay at the current position, this position is an unstable equilibrium point. Figure 8 As shown in the figure, θ = 45° is an unstable equilibrium point. The unstable equilibrium point is characterized by the centerline between two adjacent magnetic poles being aligned with the teeth. The magnetic reluctance is minimized when the magnetic field axis of the rotor permanent magnet is aligned with the stator teeth, that is, at 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°.

[0059] The attraction between the permanent magnets and the stator teeth has a circumferential component, which generates torque. This component varies nonlinearly with increasing angle from the reference position. Its maximum value is not at 52.5°, but closer to a certain position of the stator teeth. It becomes zero at 60° or 90°, which is the stable equilibrium point, as shown in the figure. Figure 9 、 10 As shown, if no significant external load is applied to the shaft, it remains permanently in this position. When the surroundings are disturbed at the stable equilibrium point, the rotor tends to align with the stator teeth to achieve the position of minimum magnetic resistance. To rotate the rotor past 90°, an external force must be applied. Therefore, by convention, it generates a negative torque.

[0060] From the knowledge of electrical machinery, we know that the relationship between the number of cogging torque cycles within a mechanical cycle and the number of slots S and poles P is as follows:

[0061] The number of cogging torque cycles N = LCM (S, P), which is the least common multiple of the number of slots and the number of poles.

[0062] The motor of the present invention is 6S4P, so the number of torque cycles N=LCM(6,4)=12.

[0063] From the above analysis, it can be seen that the stable equilibrium point of the tooth slot torque is when the center line of the magnetic steel is directly opposite to the center line of the stator tooth, that is, the locking position.

[0064] See also Figure 11 The motor of the present invention includes a bearing 1, a gasket 2, a spring 3, a bobbin 4, a stator core 5, a magnetic steel 6, a rotor core 7, a motor rotating shaft 8, a casing 9, a winding 10, a copper sleeve 11, and a back cover 12.

[0065] The rotor structure consists of a magnetic steel 6, a rotor core 7, and a motor rotating shaft 8, which respectively provide magnetic flux, magnetic circuit, and support functions;

[0066] The bobbin 4 and the stator core 5 are used to fix the winding 10 and provide a magnetic circuit.

[0067] The spring 3 and the washer 2 preload the bearing 1, the copper sleeve 11 axially positions the rotor, and the rear cover 12, the housing 9 and the bearing 1 support the rotor to rotate.

[0068] Compared with the existing technology, the method of using the tooth slot torque to locate the flat angle of the motor rotating shaft of the present invention utilizes the motor's own tooth slot positioning torque. Through a series of stator and rotor parts assembly correspondence, the rotating shaft can be locked at a specific position in the case of power failure, meeting the customer's requirements for the product's rotating shaft flat position locking position; reducing the difficulty of software-driven control of the position and improving positioning accuracy.

[0069] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any modifications, equivalent replacements and improvements made within the concept of the present invention should be included in the patent protection scope of the present invention.

Claims

1. A method for positioning the flat angle of a motor rotating shaft using cogging torque, characterized in that: The steps include: Step S1, designing and manufacturing a die head with a positioning function; In step S1, a first key and a second key are provided on the die head, and the first key and the second key are distributed at an X angle, where the X angle is the angle between the center line of the stator tooth slot and the center line of the stator tooth; Step S2, installing the stator core and the die head together and positioning the stator core; In step S2, the first key is inserted into the stator tooth slot in the stator core to position the stator core; Step S3, assembling the housing and the die head, and positioning the angle of the housing and the stator core after assembly; In step S3, a positioning notch or other feature having a positioning function that matches the second key is provided on the housing, and the positioning notch or other feature having a positioning function is assembled with the second key; Step S4, the motor rotating shaft in the rotor structure is fixed so that the flat part is aligned with the center of the magnetic pole; Step S5, assembling all assembled motor components into a finished motor; Step S6, after the motor is assembled, rotate the motor shaft one circle when the winding is not powered, and the motor shaft is locked at 12 positions of 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330° respectively.

2. The method for positioning the flat angle of the motor rotating shaft using the cogging torque according to claim 1, wherein: The number of the first keys is less than or equal to the number of stator tooth slots in the stator core, and the first keys are evenly distributed on the die head.

3. The method for positioning the flat angle of the motor rotating shaft using the cogging torque according to claim 1, wherein: In step S3, after the positioning notch or other characteristic portion with a positioning function is assembled with the second key, the stator core and the housing are fixed by gluing.

4. The method for positioning the flat angle of the motor rotating shaft using the cogging torque according to claim 3, wherein: The housing is provided with a housing mounting hole, and the housing mounting hole corresponds to the positioning notch.

5. The method for positioning the flat angle of the motor rotating shaft using the cogging torque according to claim 4, wherein: The center line of the positioning notch coincides with the center line of the stator teeth.

6. The method for positioning the flat angle of a motor rotating shaft using cogging torque according to claim 1, wherein: In step S4, there is a method for fixing the flat position of the motor rotating shaft to face the center of the magnetic pole. The rotor core itself has a positioning keyway structure, and the keyway of the motor rotating shaft faces the positioning keyway structure of the rotor core, and the angle is fixed by the positioning key.

7. The method for positioning the flat angle of a motor rotating shaft using cogging torque according to claim 1, wherein: In step S4, there is a second method for fixing the flat part of the motor rotating shaft to face the center of the magnetic pole. The rotor core does not have a positioning keyway structure, and a jig is designed to locate the flat part of the rotor core and the motor rotating shaft. The rotor core and the motor rotating shaft are respectively installed in the jig, and the motor rotating shaft and the rotor core can be fixed by glue or interference fit.

8. The method for positioning the flat angle of a motor rotating shaft using cogging torque according to claim 1, wherein: The flat position of the motor rotating shaft is aligned with the N pole or S pole position of the magnetic steel.

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