A toothed permanent magnet motor rotor and its manufacturing method

Abstract

This invention relates to a slotted permanent magnet motor rotor and its manufacturing method, belonging to the field of motor technology. The rotor includes a magnet, a bushing, and a shaft. The bushing is fitted onto the shaft, and the bushing has slotted protrusions. The magnet has a ring structure, with slotted grooves on its inner ring. The magnet is fitted onto the outer side of the bushing via the matching slotted grooves and protrusions. This invention simplifies assembly and overcomes the problems of magnet demagnetization, rotor alignment, and torque transmission in existing technologies.

Description

Technical Field

[0001] This invention relates to a slotted permanent magnet motor rotor and its manufacturing method, belonging to the field of motor technology. Background Technology

[0002] Permanent magnet motors use permanent magnets for excitation, which simplifies the motor structure and reduces processing and assembly costs. Permanent magnet brushless motors eliminate the need for slip rings and brushes, which are prone to problems, thus improving the reliability of motor operation. Currently, the permanent magnets used in permanent magnet motors have evolved to the third generation of neodymium iron boron (NdFeB) materials. NdFeB permanent magnets possess high energy product, high coercivity, and good stability, making them suitable for manufacturing miniature, high-efficiency permanent magnet devices.

[0003] Among them, bonded NdFeB materials have the advantages of high shape freedom, easy fabrication into complex magnets or thin-walled rings, high dimensional accuracy, and resistance to deformation. They are particularly advantageous for one-piece molded multi-pole rotors or stators and are widely used in micromotors. For internal rotor motors, during assembly, the inner and outer diameters of the traditional rotor's magnetic ring are annular structures, while the outer diameter of the shaft is cylindrical, and the two are fixed together using industrial adhesives. During operation, the motor generates torque through the interaction of the alternating magnetic field of the windings and the rotor magnetic ring. This torque is transmitted to the shaft via the industrial adhesive and then output. However, in practical applications, the following problems have been found:

[0004] 1. Bonded NdFeB magnetic rings have low coercivity. During motor operation, the weak magnetic transition zone between each magnetic pole is easily affected by temperature and external alternating magnetic fields, resulting in demagnetization and affecting the normal operation of the motor.

[0005] 2. The inner ring of the magnetic ring is circular and is fixed to the shaft with industrial adhesive. Due to insufficient bonding area and insufficient rigidity of the adhesive, the adhesive will loosen when subjected to large loads or vibrations, causing the magnetic ring to fall off due to relative displacement between the magnetic ring and the shaft.

[0006] 3. The magnetic ring is circumferentially positioned using an industrial adhesive with a clearance fit to the shaft. During assembly, the adhesive is fluid before solidification, which can cause the motor shaft and the magnet to shift, affecting the motor's alignment and increasing operating noise and vibration.

[0007] To address the aforementioned technical problems, this invention is proposed. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a slotted permanent magnet motor rotor that is simple to assemble and can overcome the problems of magnet demagnetization, rotor alignment, and torque transmission in existing technologies.

[0009] The present invention also provides a method for manufacturing the above-mentioned slotted permanent magnet motor rotor.

[0010] The technical solution of the present invention is as follows:

[0011] A slotted permanent magnet motor rotor includes a magnet, a bushing, and a shaft. The bushing is fitted onto the shaft and has slotted protrusions. The magnet has an annular structure and a slotted groove is provided on the inner ring of the magnet. The magnet is fitted onto the outer side of the bushing through the matching of the slotted groove and the slotted protrusion.

[0012] The combination of toothed grooves and toothed protrusions can play a role in centering and positioning, reducing centering errors and ensuring high alignment between the magnet and the bushing. This can reduce axial eccentricity between the motor rotor and stator, avoid electromagnetic noise caused by excessively small air gaps or inconsistent lengths, and also prevent the stator and rotor from rubbing against each other under high-speed and heavy-load conditions when eccentricity is severe, which can cause severe vibration and uneven friction noise in the motor.

[0013] Meanwhile, the magnet uses a toothed groove inside. Compared with the traditional ring-shaped set, the thickened magnet has a larger magnetomotive force and a larger internal magnetic resistance. When facing the same demagnetizing magnetomotive force, it has a strong resistance to demagnetization. Therefore, the toothed groove structure can reduce the demagnetization at this position.

[0014] According to a preferred embodiment of the present invention, a top sleeve and a baffle are respectively provided on the rotating shafts on both sides of the magnet. The top sleeve and the baffle limit the magnet and the bushing along the axial direction to prevent vibration and temperature rise from causing the adhesive to fail and the magnet and the core to undergo axial displacement.

[0015] According to a preferred embodiment of the present invention, the rotating shaft is a stepped shaft, which facilitates axial positioning of components such as bushings. The rotating shaft is provided with a keyway, and a flat key is provided in the keyway. The bushing is provided with a groove that matches the flat key. The rotating shaft is fitted with the bushing through the keyway and the flat key, and the flat key is used to transmit torque.

[0016] According to a preferred embodiment of the present invention, the magnet is a neodymium iron boron magnet, and the bonding process can effectively improve dimensional accuracy and processing efficiency.

[0017] According to a preferred embodiment of the present invention, the magnet is radially magnetized, and the radial magnetic field strength after magnetization is a saddle waveform, with the magnet forming N poles and S poles alternately in the circumferential direction.

[0018] According to a preferred embodiment of the present invention, the angle θ1 between the top of the tooth groove in the magnet and the axis is greater than the angle θ of the magnetic pole transition zone, where θ = 180° × (1 - ap) / p, and ap is the pole arc coefficient and p is the number of pole pairs. This arrangement ensures that the tooth groove structure covers all positions of the magnetic pole transition zone, enhancing its resistance to demagnetization.

[0019] According to a preferred embodiment of the present invention, in order to ensure that the motor obtains a sufficiently high air gap magnetic flux density, the magnet thickness is... Among them, K u K is the saturation coefficient. cμ is the air gap coefficient, g is the air gap magnetic flux density length, and μ is the air gap coefficient. r denoted as ρ, where ρ is the relative permeability of the magnet.

[0020] According to a preferred embodiment of the present invention, the adhesive zone between the magnet and the bushing is provided with a clearance fit of H9 / h9 or lower based on the hole basis system, which can be used to apply adhesive, effectively prevent the rotor core from loosening due to high torque, and improve processing efficiency. The positioning zone between the magnet and the bushing is provided with a clearance fit of H7 / h6 or higher based on the hole basis system, which is used for centering and positioning, and prevents the core magnet from being eccentric during the adhesive solidification stage.

[0021] According to a preferred embodiment of the present invention, the top sleeve includes two hollow cylinders with different diameters. The larger diameter end of the top sleeve axially positions the magnet and the bushing, while the smaller diameter end positions the motor selection bearing. The outer diameter of the smaller diameter end is smaller than the inner ring diameter of the bearing, which facilitates bearing disassembly.

[0022] The manufacturing method of the above-mentioned slotted permanent magnet motor rotor includes the following steps:

[0023] (1) The magnet material is neodymium iron boron material. It is made by mixing neodymium iron boron powder and pressing it in a mold of matching shape. After pressing, it is cured at high temperature and surface treated. The processing is simple and suitable for mass production. The pressed magnet does not have magnetism. Then the magnet is placed in a magnetizer for magnetization. During the magnetization process, the top of the tooth groove in the magnet is located in the magnetic pole transition area, and the bottom of the tooth groove is located in the N pole and S pole position. In this way, the thickened tooth groove position can protect the low coercivity magnetic pole transition area and prevent it from demagnetizing.

[0024] (2) The bushing is made of magnetic metal by turning and milling. During assembly, the inner ring of the magnet is first coated with industrial adhesive, and then the bushing is fitted into the inner ring of the magnet according to the tooth profile. At this time, the positioning position on the bushing is matched with the magnet with a very small gap. The positioning of the tooth groove can ensure the high alignment of the magnet and the bushing in the radial direction and fix them to ensure that the magnet and the bushing will not be eccentric due to the extrusion and flow of the adhesive or human movement while waiting for the adhesive to solidify.

[0025] (3) After the adhesive between the magnet and the bushing solidifies, first put the baffle into the shaft, then install the flat key. After the flat key is installed, put the bushing into the shaft until it contacts the baffle. At this time, the magnet will automatically attract the baffle with its own magnetism. Finally, install the top sleeve. The larger outer diameter of the top sleeve is installed into the shaft first until it contacts the magnet, while the other side is limited by the motor bearing.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. The present invention has a simple structure and ingenious design. It can effectively position the assembly of the magnet and the bushing through a toothed groove structure, thereby improving production efficiency.

[0028] 2. During the machining process, the bushing tooth groove of the present invention achieves the dual effects of applying adhesive and positioning by setting machining tolerances.

[0029] 3. The top sleeve and baffle of the present invention position the rotor core, which facilitates assembly, is suitable for mass production, improves production efficiency, and prevents axial movement of the bushing and magnet.

[0030] 4. The magnetic steel tooth groove angle created by this invention, verified by finite element simulation, can effectively reduce demagnetization during operation and improve operational stability. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the present invention.

[0032] Figure 2 This is a schematic diagram of the split structure of the present invention.

[0033] Figure 3 This is a schematic cross-sectional view of the structure of the present invention.

[0034] Figure 4 This is a side view structural diagram of the present invention.

[0035] Figure 5 This invention follows Figure 4 The diagram shows a cross-sectional view along direction A.

[0036] Figure 6 This is a schematic diagram of the magnetic ring structure of the present invention.

[0037] Figure 7 This is a schematic diagram of the bushing structure of the present invention.

[0038] Figure 8 This is a demagnetization rate cloud map of the present invention and existing conventional magnets.

[0039] Diagram description: 1-Magnet, 2-Sleeve, 3-Shaft, 4-Top sleeve, 5-Key, 6-Baffle plate

[0040] 11-Gate top, 12-Gate bottom,

[0041] 21-Positioning area, 22-Adhesive area, 23-Groove. Detailed Implementation

[0042] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0043] Example 1:

[0044] like Figure 1-7 As shown, this embodiment provides a slotted permanent magnet motor rotor, including a magnet 1, a bushing 2, and a rotating shaft 3. The bushing 2 is fitted onto the rotating shaft 3, and the bushing 2 is provided with slotted protrusions. The magnet 1 has an annular structure, and the inner ring of the magnet 1 is provided with slotted grooves. The magnet 1 is fitted onto the outer side of the bushing 2 through the matching of the slotted grooves and slotted protrusions.

[0045] The combination of toothed grooves and toothed protrusions can play a role in centering and positioning, reducing centering errors and ensuring high alignment between the magnet and the bushing. This can reduce axial eccentricity between the motor rotor and stator, avoid electromagnetic noise caused by excessively small air gaps or inconsistent lengths, and also prevent the stator and rotor from rubbing against each other under high-speed and heavy-load conditions when eccentricity is severe, which can cause severe vibration and uneven friction noise in the motor.

[0046] Meanwhile, the magnet uses a toothed groove inside. Compared with the traditional ring-shaped set, the thickened magnet has a larger magnetomotive force and a larger internal magnetic resistance. When facing the same demagnetizing magnetomotive force, it has a strong resistance to demagnetization. Therefore, the toothed groove structure can reduce the demagnetization at this position.

[0047] Top sleeves 4 and baffles 6 are respectively provided on the rotating shafts 3 on both sides of the magnet 1. The top sleeves 4 and baffles 6 limit the magnet and the bushing along the axial direction to prevent vibration and temperature rise from causing the adhesive to fail and the magnet and the core to undergo axial displacement.

[0048] The rotating shaft 3 is a stepped shaft, which facilitates axial positioning of components such as bushings. The rotating shaft 3 is provided with a keyway, and a flat key 5 is provided in the keyway. The bushing 2 is provided with a groove 23 that matches the flat key. The rotating shaft 3 is fitted with the bushing 2 through the keyway and the flat key 5, and the torque is transmitted by the flat key.

[0049] Magnet 1 uses neodymium iron boron magnets, and the bonding process can effectively improve dimensional accuracy and processing efficiency.

[0050] The magnet 1 is radially magnetized, and the radial magnetic field strength after magnetization is a saddle waveform. The magnet alternately forms N poles and S poles in the circumference. The main magnetic area is located at the bottom of the tooth groove 12, and the transition area between magnetic poles is located at the top of the tooth groove 11.

[0051] To ensure the motor achieves a sufficiently high air gap magnetic flux density, the thickness of magnet 1 is... Among them, K u K is the saturation coefficient. c μ is the air gap coefficient, g is the air gap magnetic flux density length, and μ is the air gap coefficient. r K represents the relative permeability of the magnet (1.05–1.10 for NdFeB). In this embodiment, K is taken as... u =1.5~2, K c =1.2, μ r Substituting h = 1.05 to 1.10 and g = 0.5, we obtain the magnet thickness range h.m =2.5~6.7. In order to ensure that the tooth groove thickness can play an anti-demagnetization role and at the same time meet the thickness range of the magnet, the upper limit of the thickness of the groove of the magnet 1 is taken as 6.7mm.

[0052] The manufacturing method of the above-mentioned slotted permanent magnet motor rotor includes the following steps:

[0053] (1) The magnet material is neodymium iron boron material. It is made by mixing neodymium iron boron powder and pressing it in a mold of matching shape. After pressing, it is cured at high temperature and surface treated. The processing is simple and suitable for mass production. The pressed magnet does not have magnetism. Then the magnet is placed in a magnetizer for magnetization. During the magnetization process, the top of the tooth groove in the magnet is located in the magnetic pole transition area, and the bottom of the tooth groove is located in the N pole and S pole position. In this way, the thickened tooth groove position can protect the low coercivity magnetic pole transition area and prevent it from demagnetizing.

[0054] (2) The bushing is made of magnetic metal by turning and milling. During assembly, the inner ring of the magnet is first coated with industrial adhesive, and then the bushing is fitted into the inner ring of the magnet according to the tooth profile. At this time, the positioning position on the bushing is matched with the magnet with a very small gap. The positioning of the tooth groove can ensure the high alignment of the magnet and the bushing in the radial direction and fix them to ensure that the magnet and the bushing will not be eccentric due to the extrusion and flow of the adhesive or human movement while waiting for the adhesive to solidify.

[0055] (3) After the adhesive between the magnet and the bushing solidifies, first put the baffle into the shaft, then install the flat key. After the flat key is installed, put the bushing into the shaft until it contacts the baffle. At this time, the magnet will automatically attract the baffle with its own magnetism. Finally, install the top sleeve. The larger outer diameter of the top sleeve is installed into the shaft first until it contacts the magnet, while the other side is limited by the motor bearing.

[0056] Example 2:

[0057] A slotted permanent magnet motor rotor, with the structure described in Embodiment 1, differs in that the angle θ1 of the slot top 11 position relative to the shaft center within the magnet 1 is greater than the angle θ of the magnetic pole transition zone, where θ = 180° × (1 - ap) / p, where ap is the pole arc coefficient and p is the number of pole pairs. This arrangement ensures that the slotted structure covers all positions of the magnetic pole transition zone, enhancing its demagnetization resistance. The pole arc coefficient is 0.83-0.88 during actual magnetization. For the 4-pole magnet in this embodiment, the angle θ of each magnetic pole transition zone is 180° × (1 - 0.85) / 2 = 13.5°.

[0058] Figure 8 The figure shows a comparison of the demagnetization rates of the toothed magnet of the present invention and the conventional magnet under the same working conditions. Figure 8(a) represents the demagnetization rate of the toothed magnet of the present invention. Figure 8 (b) represents the demagnetization rate of conventional magnets; the darker the color in the figure, the more severe the demagnetization. By comparison, the dark area of ​​the toothed magnet of the present invention is significantly reduced compared to conventional magnets, indicating that the toothed magnet of the present invention exhibits lower demagnetization and better resistance to demagnetization compared to conventional magnets.

[0059] Example 3:

[0060] A toothed permanent magnet motor rotor, with the structure described in Embodiment 1, differs in that the adhesive region 22 between the magnet and the bushing has a clearance fit of H9 / h9 or lower, which can be used to apply the adhesive, effectively preventing rotor core loosening caused by high torque and improving processing efficiency. The positioning region 21 between the magnet and the bushing has a clearance fit of H7 / h6 or higher, which is used for centering and positioning, preventing core-magnet eccentricity during the adhesive solidification stage. The adhesive region 22 is the toothed protrusion sidewall on the bushing and the corresponding position on the magnet; the remaining positions are the positioning region 21.

[0061] Example 4:

[0062] A toothed permanent magnet motor rotor, with the structure described in Embodiment 1, differs in that the top sleeve 4 comprises two hollow cylinders of different diameters. The larger diameter end of the top sleeve axially positions the magnet and the bushing, while the smaller diameter end positions the motor select bearing. The outer diameter of the smaller diameter end is smaller than the inner ring diameter of the bearing, facilitating bearing disassembly. The baffle is a mass-produced part used for axial positioning of the bushing and the magnet, preventing displacement between the magnetic ring and the bushing.

Claims

1. A cogged permanent magnet machine rotor, characterized by, The utility model relates to a magnetic steel, shaft sleeve and rotating shaft, wherein the rotating shaft is sleeved with the shaft sleeve, the shaft sleeve is provided with a tooth groove type protrusion, the magnetic steel is annular, the inner ring of the magnetic steel is provided with a tooth groove type groove, and the magnetic steel is matched and sleeved outside the shaft sleeve through the tooth groove type groove and the tooth groove type protrusion. The rotating shaft is a stepped shaft, the rotating shaft is provided with a key groove, the key groove is provided with a flat key, the shaft sleeve is provided with a slot matching the flat key, and the rotating shaft is sleeved with the shaft sleeve through the key groove and the flat key. The magnetic steel adopts a neodymium iron boron magnet, the magnetic steel is radially magnetized, the radial magnetic field strength after magnetization is a saddle wave shape, and the magnetic steel alternately forms N and S poles in the circumferential direction. The angle theta1 of the tooth groove top position in the magnetic steel relative to the shaft center is greater than the magnetic pole transition zone angle theta, and theta=180°* (1-ap) / p, wherein ap is a pole arc coefficient, and p is a pole number. Magnet thickness where K u is the saturation coefficient, K c is the air gap coefficient, g is the air gap flux length, μ r is the relative permeability of the magnet.

2. The slotted permanent magnet machine rotor of claim 1, wherein, The rotating shaft on both sides of the magnetic steel is respectively provided with a top sleeve and a baffle.

3. The tooth-slot permanent magnet motor rotor of claim 1, wherein, The adhesive area between the magnetic steel and the shaft sleeve is provided with a gap fit of base hole H9 / h9 and below, and the positioning area between the magnetic steel and the shaft sleeve is provided with a gap fit of base hole H7 / h6 and above.

4. The slotted permanent magnet machine rotor of claim 1, wherein, The top sleeve includes two hollow cylinders with different diameters, and the large diameter end of the top sleeve axially positions the magnetic steel and the shaft sleeve.

5. A method of manufacturing a rotor for a tooth-slot permanent magnet machine according to any one of claims 1 to 4, characterized in that, The steps are as follows: (1) The magnetic steel material is made of neodymium iron boron material and is pressed in a mold, then high-temperature solidification and surface treatment are carried out, and then the magnetic steel is placed in a magnetizer for magnetization. During the magnetization process, the tooth groove top in the magnetic steel is located at the magnetic pole transition zone position, and the tooth groove bottom is located at the N and S pole positions. (2) During assembly, the inner ring of the magnetic steel is coated with industrial adhesive, and then the shaft sleeve is sleeved into the inner ring of the magnetic steel according to the tooth shape fit; (3) After the adhesive between the magnetic steel and the shaft sleeve solidifies, the baffle is sleeved into the rotating shaft, then the flat key is installed, the shaft sleeve is sleeved into the rotating shaft after the flat key is installed until the baffle is contacted, at this time, the magnetic steel is automatically adsorbed with the baffle by using its own magnetism, and finally the top sleeve is installed.

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