High speed motor rotor structure with optimized interference

Abstract

The application discloses a high-speed motor rotor structure with optimized interference amount, and belongs to the technical field of motor rotors. The high-speed motor rotor structure with optimized interference amount comprises a permanent magnet shaft section in the middle, a core shaft section concentrically connected to left and right ends of the permanent magnet shaft section, and a magnetic bearing interference-assembled outside shaft ends of the core shaft section; and a centrifugal force deformation hole coaxially arranged at the center of the core shaft section and extending from the permanent magnet shaft section to a position area of the magnetic bearing. The high-speed motor rotor structure with optimized interference amount is used in a magnetic suspension motor. Through the design of the centrifugal force deformation hole at the center of the core shaft section, part of centrifugal stress is released by radial deformation of the hole during high-speed rotation, so that a smaller initial interference amount is allowed without causing excessive attenuation of surface pressure, and meanwhile, structural strength and mass production adaptability are considered.

Description

Technical Field

[0001] This invention relates to the field of motor rotor technology, specifically to a high-speed motor rotor structure with optimized interference fit. Background Technology

[0002] As a core power component of high-end equipment, the rotor of a magnetic levitation motor must maintain high rigidity, low vibration, and stable interference fit under high-speed rotation (e.g., 1-5 rpm). Traditional magnetic levitation motor rotors typically consist of a permanent magnet shaft section, a spindle section, and magnetic bearings. The magnetic bearings and spindle section are connected by an interference fit to transmit torque and constrain radial displacement. However, as the rotational speed increases, the magnetic bearing assembly and spindle experience radial expansion. Furthermore, the magnetic bearing rotor assembly has relatively low rigidity, resulting in greater radial deformation. This leads to a decrease in the surface pressure at the interference surface between the spindle and the magnetic bearing, as shown in the attached figure. Figure 1 As shown ( Figure 1 For the un-drilled model: equivalent stress and residual surface pressure values. As can be seen from the figure: when the interference is 0.14, the surface pressure at the contact surface is 0. The interference is too small and does not meet the requirements. When the interference is 0.18, the equivalent stress is 390 MPa, exceeding the material's yield strength and not meeting the strength requirements. The lower limit of the interference is 0.15, and the upper limit is 0.17, a range of only two micrometers, which does not meet the requirement of 4 micrometers for mass production. (Excessive surface pressure attenuation may lead to fit failure, increased vibration, or even equipment damage).

[0003] Traditional solutions compensate for centrifugal relaxation by increasing the initial interference, but this is limited by material strength (the silicon steel sheets of the rotor assembly undergo plastic deformation due to excessive interference, affecting control accuracy) and processing precision (micron-level interference is difficult to control stably). There is an upper limit to the increase in interference, making it difficult to meet the requirements of higher speeds (such as ≥40,000 rpm), which is not conducive to mass production. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-speed motor rotor structure with optimized interference fit, which is used in magnetic levitation motor. By designing a centrifugal force deformation hole at the center of the spindle section, the radial deformation of the hole is used to release part of the centrifugal stress during high-speed rotation, thereby allowing a smaller initial interference fit without causing insufficient rotor pressure at high speed, while taking into account structural strength and mass production adaptability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A high-speed motor rotor structure with optimized interference fit includes a permanent magnet shaft section located in the middle, a spindle section concentrically connected to the left and right ends of the permanent magnet shaft section, and a magnetic bearing interference-fitted to the outer side of the shaft end of the spindle section; the center of the spindle section is coaxially provided with a centrifugal force deformation hole extending from the permanent magnet shaft section to the magnetic bearing position area, and the centrifugal stress distribution is adjusted by the radial deformation of the centrifugal force deformation hole, thereby optimizing the interference fit performance.

[0007] By adopting the above scheme, the high-speed motor rotor structure with optimized interference releases part of the centrifugal stress through the radial deformation of the centrifugal force deformation hole. While ensuring that the surface pressure does not decrease excessively, it allows the initial interference to be reduced by 5-15%, solving the problem of insufficient rotor component strength caused by excessive interference. It is suitable for magnetic levitation motors with higher speeds (≥40,000 rpm). By adjusting the diameter of the deformation hole, it can be adapted to rotors with different speed requirements, and has a certain degree of mass production adaptability.

[0008] As a preferred embodiment of a high-speed motor rotor structure with optimized interference fit, the diameter of the centrifugal force deformation hole is 0.3-0.4 times the minimum diameter of the mandrel section. This size range is optimized based on the centrifugal expansion characteristics of the material: a smaller centrifugal force deformation hole diameter (≤0.3 times) cannot effectively release stress; a larger diameter (≥0.4 times) will significantly reduce the stiffness of the mandrel section, leading to a decrease in the rotor's critical speed. The presence of the deformation hole causes the area around the hole to expand radially outward due to centrifugal force when the mandrel section rotates at high speed (deformation Δr≈k·ρ·ω²·r²·D1 / (4E), where k is the shape factor, ρ is the material density, ω is the angular velocity, r is the radius of rotation, and E is the elastic modulus), thereby releasing part of the centrifugal stress at the contact interface between the mandrel section and the magnetic bearing, allowing the initial interference fit to be reduced by 5-15% (compared to the traditional structure without deformation holes).

[0009] In a preferred embodiment of a high-speed motor rotor structure with optimized interference fit, the inner wall of the centrifugal deformation hole is covered with a metal layer with a density higher than that of the mandrel section, such as a high-density tungsten-based alloy (density 17-19 g / cm³) or lead alloy (11.3 g / cm³), which has a density greater than that of the mandrel section made of alloy steel (density 7.9 g / cm³). The metal layer is 1-3 mm thick and bonded to the inner wall of the deformation hole via thermal spraying (e.g., plasma spraying) or electroplating (e.g., nickel plating), with a bonding strength ≥50 MPa. During high-speed rotation, the centrifugal stress of the metal layer amplifies the radial deformation of the mandrel section, thereby reducing excessive attenuation of the pressure under high speeds.

[0010] As a preferred embodiment of the high-speed motor rotor structure with optimized interference fit, the centrifugal deformation hole is filled with a thermal expansion material that completely seals it and has a higher coefficient of thermal expansion than the mandrel section. The thermal expansion material is a high-expansion alloy steel (such as FeNi3Mn7 or Mn72Cr18Ni10 alloy), and the coefficient of thermal expansion of the mandrel section is 11×10⁻. 6 The coefficient of thermal expansion of FeNi3Mn7 or Mn72Cr18Ni10 alloys is 21 × 10⁻ / ℃. 6 / ℃. The function of the thermal expansion material is: after the rotor is assembled, the thermal expansion material expands due to heat (from room temperature to working temperature) and fully squeezes outward the centrifugal deformation hole. Under the action of centrifugal force, the radial deformation of the mandrel section increases, further reducing the excessive attenuation of surface pressure.

[0011] As a preferred embodiment of the high-speed motor rotor structure with optimized interference fit, the spindle section has multiple circumferentially arrayed heat dissipation holes on the surface of the magnetic bearing location area, which are oriented towards the centrifugal force deformation holes. The number of heat dissipation holes is 6-10, the diameter is 0.5-2mm, and the depth is 1 / 5-1 / 4 of the radius of the spindle section. All heat dissipation holes are close to the centrifugal force deformation holes but are not connected to them. Because the heat dissipation holes are oriented towards the deformation holes but are not connected, the airflow can be guided to flow towards the centrifugal force deformation holes, thereby enhancing the heat exchange efficiency and promoting the full heating of the thermal expansion material.

[0012] In a preferred embodiment of a high-speed motor rotor structure with optimized interference fit, the end face of the mandrel section facing the permanent magnet section has multiple circumferentially arrayed filling holes extending to the magnetic bearing location area. The number of filling holes is 2-6, with a diameter of 1-3 mm. Each filling hole is filled and fixed with a metal core of higher density than the mandrel section. The metal core is made of high-density tungsten-based alloy (density 17-19 g / cm³) or lead alloy (11.3 g / cm³), and is fixed to the filling hole by interference fit (interference fit 0.01-0.05 mm). During high-speed rotation, the centrifugal stress of the metal core expands, causing radial deformation of the mandrel section and releasing some of the centrifugal stress, thereby further reducing excessive surface pressure attenuation.

[0013] In a preferred embodiment of a high-speed motor rotor structure with optimized interference fit, multiple circumferentially arrayed filling grooves extending from the permanent magnet shaft section to the magnetic bearing location area are formed on the outer surface of the spindle section. The number of filling grooves is 2-6, and the grooves are rectangular in shape. Each filling groove is filled with a metal strip of higher density than the spindle section and matching the outer surface of the spindle section. The metal strip is made of the same material as the metal core and is fixed to the filling groove by embedded fixing (such as adhesive bonding), with a fit ≥95%. During high-speed rotation, the centrifugal stress of the metal strip will increase, causing radial deformation of the spindle section and releasing some of the centrifugal stress, thereby further reducing excessive surface pressure attenuation.

[0014] As a preferred embodiment of the high-speed motor rotor structure with optimized interference fit, in order to improve the overall rigidity and corrosion resistance of the rotor, a protective sleeve is also included, which is interference-fitted on the outside of the permanent magnet shaft section and the outside of the spindle sections at both ends. The protective sleeve is made of high-strength alloy, and the interference fit with the permanent magnet shaft section and the spindle section is 0.02-0.1mm. The axial length covers 60-70% of the total length of the permanent magnet shaft section and the spindle section.

[0015] As a preferred embodiment of the high-speed motor rotor structure with optimized interference fit, the centrifugal deformation hole in the area where the protective sleeve is located is called centrifugal deformation hole one, and the centrifugal deformation hole in the area where the magnetic bearing is located is called centrifugal deformation hole two. The diameter of centrifugal deformation hole two is greater than or equal to the diameter of centrifugal deformation hole one, and the diameter difference is 5-20% of that of centrifugal deformation hole one. The reason for the partitioned design is that the interference fit area between the magnetic bearing and the spindle section is sensitive to deformation (requiring precise control of surface pressure), while the spindle section area covered by the protective sleeve has higher rigidity and allows for a larger amount of deformation.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. Optimized interference range: By releasing part of the centrifugal stress through the radial deformation of the centrifugal force deformation hole, while ensuring that the surface pressure does not decay excessively, the initial interference is allowed to be reduced by 5-15%, which solves the problem of insufficient rotor assembly strength caused by excessive interference and is suitable for magnetic levitation motors with higher speeds (≥40,000 rpm).

[0018] 2. Further reduce surface pressure attenuation: By adding metal layers, thermal expansion materials, metal cores or metal strips, surface pressure attenuation under high-speed rotation is reduced.

[0019] 3. Enhanced structural reliability: The addition of heat dissipation holes, which face the deformation holes but are not connected, can guide airflow to the centrifugal deformation holes, enhance heat exchange efficiency, and promote the full and uniform heating of thermally expanding materials.

[0020] 4. Facilitates mass production: This solution can reduce the lower limit of interference and can meet the requirement of upper limit - lower limit > 4 mil under extreme conditions, without the need for grinding installation, thus meeting the requirements of mass production. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The background technology shows the equivalent force diagram of the interference fit between the traditional mandrel and the magnetic bearing.

[0023] Figure 2 This is a cross-sectional view of the high-speed motor rotor structure with optimized interference fit in Example 1;

[0024] Figure 3 for Figure 2 Partial structural diagram;

[0025] Figure 4 This is a longitudinal cross-sectional view of the high-speed motor rotor structure with optimized interference fit in Example 1;

[0026] Figure 5 This is an equivalent stress diagram of the interference fit between the conventional mandrel and the magnetic bearing in Example 1.

[0027] Figure 6 This is a longitudinal cross-sectional view of the high-speed motor rotor structure with optimized interference fit in Example 2;

[0028] Figure 7 This is a longitudinal cross-sectional view of the high-speed motor rotor structure with optimized interference fit in Example 3;

[0029] Figure 8 This is a longitudinal cross-sectional view of the high-speed motor rotor structure with optimized interference fit in Example 4;

[0030] Figure 9 This is a longitudinal cross-sectional view of the high-speed motor rotor structure with optimized interference fit in Example 5;

[0031] The markings in the diagram are: 1-Magnetic bearing; 2-Mandrel section; 2-1 Centrifugal deformation hole; 3-Protective sleeve; 4-Permanent magnet shaft section; 5-Metal layer; 6-Thermal expansion material; 7-Heat dissipation hole; 8-Metal core; 9-Metal strip. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1, as Figures 2 to 5As shown, a high-speed motor rotor structure with optimized interference fit is provided for use in a magnetic levitation motor. Specifically, it includes a permanent magnet shaft section 4 (samarium cobalt) located in the middle, a spindle section 2 (alloy steel) concentrically connected to the left and right ends of the permanent magnet shaft section 4, a magnetic bearing 1 (silicon steel sheet) interference-fitted to the outer side of the spindle section 2 shaft end, and a protective sleeve 3 interference-fitted to the outer side of the permanent magnet shaft section 4 and the outer side of the spindle section 2 shaft at both ends. The protective sleeve 3 is made of a high-strength alloy, but can also be a carbon fiber composite material (density 1.8 g / cm³). The interference fit with the permanent magnet shaft section 4 and the spindle section 2 is 0.05 mm, and the axial length covers 65% of the total length of the permanent magnet shaft section 4 and the spindle section 2, which can be within the range of 60-70%. A centrifugal force deformation hole is coaxially provided at the center of the spindle section 2, extending from the permanent magnet shaft section 4 to the location of the magnetic bearing 1. The radial deformation of this centrifugal force deformation hole optimizes the interference fit performance. This optimized high-speed motor rotor structure reduces surface pressure attenuation at high speeds through radial deformation of the centrifugal force deformation hole, allowing the initial interference to be reduced by 5-15%. Figure 5 As shown ( Figure 5 The open-hole model has a lower limit of interference of 0.12 and an upper limit of interference of 0.16. When the interference is at the lower limit, the surface pressure is >0, and when the interference is at the upper limit, it does not exceed the material yield strength and meets the mass production requirements of 4 mils. This solves the problem of the lower limit of interference caused by centrifugal relaxation in traditional structures and is suitable for magnetic levitation motors with higher speeds (≥40,000 rpm). By adjusting the diameter of the deformable hole, it can be adapted to rotors with different speed requirements and has a certain degree of mass production adaptability.

[0034] like Figure 4 As shown, the centrifugal deformation hole is 0.3-0.4 times the minimum diameter of the mandrel segment. This size range is optimized based on the centrifugal expansion characteristics of the material: a smaller centrifugal deformation hole diameter (≤0.3 times) cannot effectively release stress; a larger diameter (≥0.4 times) will significantly reduce the stiffness of the mandrel segment 2, leading to a decrease in the rotor's critical speed. The presence of the deformation hole causes the area around the hole to expand radially outward due to centrifugal force when the mandrel segment 2 rotates at high speed (deformation Δr≈k·ρ·ω²·r²·D1 / (4E), where k is the shape factor, ρ is the material density, ω is the angular velocity, r is the radius of rotation, and E is the elastic modulus), thereby releasing part of the centrifugal stress at the contact interface between the mandrel segment 2 and the magnetic bearing 1, allowing the initial interference to be reduced by 5-15% (compared to the traditional structure without deformation holes).

[0035] like Figures 2 to 3As shown, the centrifugal deformation hole in the area where the protective sleeve 3 is located is called centrifugal deformation hole one, and the centrifugal deformation hole in the area where the magnetic bearing 1 is located is called centrifugal deformation hole two. The diameter of centrifugal deformation hole two is equal to the diameter of centrifugal deformation hole one. Of course, the diameter of centrifugal deformation hole two can also be larger than the diameter of centrifugal deformation hole one, with the diameter difference being 5-20% of that of centrifugal deformation hole one. The reason for the partitioned design is that the interference fit area between the magnetic bearing 1 and the spindle section 2 is sensitive to deformation (requiring precise control of surface pressure), while the area of ​​spindle section 2 covered by the protective sleeve 3 has higher rigidity, allowing for a larger amount of deformation.

[0036] Example 2, as Figure 6 As shown, the difference between this embodiment and Embodiment 1 lies only in that, based on Embodiment 1, a metal layer 5 with a density higher than that of the mandrel segment 2 is applied to the inner wall of the centrifugal deformation hole. This metal layer 5 is a high-density tungsten-based alloy (density 17-19 g / cm³), or it could be a lead alloy (11.3 g / cm³), with a density greater than that of the stainless steel (density 7.9 g / cm³) mandrel segment 2. The thickness is 1-3 mm. This layer is bonded to the inner wall of the deformation hole using a thermal spraying (plasma spraying) process, or it could be electroplated (such as nickel plating), with a bonding strength ≥ 50 MPa. During high-speed rotation, the centrifugal stress of the metal layer 5 will increase, causing radial deformation of the mandrel segment 2 and releasing some of the centrifugal stress, thereby further reducing excessive surface pressure attenuation.

[0037] Example 3, as Figure 7 As shown, the difference between this embodiment and Embodiment 1 is only that, based on Embodiment 1, the centrifugal deformation hole is filled with a thermal expansion material 6 that completely seals it and has a thermal expansion coefficient higher than that of the mandrel section 2. The thermal expansion material 6 is a high-expansion alloy steel (such as FeNi3Mn7 or Mn72Cr18Ni10, etc.), and the mandrel section 2 is an alloy steel with a thermal expansion coefficient of 11×10⁻. 6 At / ℃, the coefficient of thermal expansion of FeNi3Mn7 or Mn72Cr18Ni10 is 21×10⁻ 6 / ℃. The function of thermal expansion material 6 is: after thermal expansion (from room temperature to working temperature), thermal expansion material 6 fully squeezes the centrifugal deformation hole, which will expand the radial deformation of the mandrel section 2, thereby reducing the excessive attenuation of surface pressure.

[0038] Continue as Figure 7As shown, multiple circumferentially arrayed heat dissipation holes 7 are formed on the surface of the mandrel segment 2 in the region of the magnetic bearing 1, facing the centrifugal force deformation hole. The number of heat dissipation holes 7 is 6, which can be in the range of 6-10. The depth is 1 / 5 of the radius of the mandrel segment 2, which can be in the range of 1 / 5-1 / 4. All heat dissipation holes 7 are close to the centrifugal force deformation hole but are not connected to it. Because the heat dissipation holes 7 face the deformation hole but are not connected, they can guide the airflow to flow to the centrifugal force deformation hole, enhance the heat exchange efficiency, and promote the thermal expansion material 6 to be fully heated.

[0039] Example 4, as Figure 8 As shown, the difference between this embodiment and Embodiment 1 is only that, based on Embodiment 1, multiple circumferentially arrayed filling holes are formed on the end face of the mandrel segment 2 facing the permanent magnet shaft segment 4, extending to the location of the magnetic bearing 1. The number of filling holes is 6, which can be in the range of 2-6. Each filling hole is filled and fixed with a metal core 8 with a density higher than that of the mandrel segment 2. The material of the metal core 8 is a high-density tungsten-based alloy (density 17-19 g / cm³), or it can be a lead alloy (11.3 g / cm³). It is fixed to the filling hole by interference fit (interference amount 0.03 mm). During high-speed rotation, the centrifugal stress of the metal core 8 will increase the radial deformation of the mandrel segment 2 to release part of the centrifugal stress, thereby further reducing the excessive attenuation of surface pressure.

[0040] Example 5, as Figure 9 As shown, the difference between this embodiment and Embodiment 1 is that, based on Embodiment 1, multiple circumferentially arrayed filling grooves are formed on the outer surface of the mandrel segment 2, extending from the permanent magnet shaft segment 4 to the magnetic bearing 1 location area. The number of filling grooves is 4, and can be in the range of 2-6. The filling grooves are rectangular in shape, and each filling groove is filled with a metal strip 9 with a density higher than that of the mandrel segment 2 and matching the outer surface of the mandrel segment 2. The material of the metal strip 9 is the same as that of the metal core 8, and it is fixed to the filling groove by embedded fixing (adhesive bonding), with a fitting degree ≥95%. During high-speed rotation, the centrifugal stress of the metal strip 9 will increase the radial deformation of the mandrel segment 2 to release part of the centrifugal stress, thereby further reducing the excessive attenuation of surface pressure.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-speed motor rotor structure with optimized interference fit, comprising a permanent magnet shaft section located in the middle, a spindle section concentrically connected to the left and right ends of the permanent magnet shaft section, and a magnetic bearing interference-fitted to the outer side of the spindle section shaft end; Its features are: The mandrel section is coaxially provided with a centrifugal force deformation hole extending from the permanent magnet shaft section to the magnetic bearing position area; The inner wall of the centrifugal deformation hole is covered with a metal layer with a density higher than that of the mandrel section. The end face of the mandrel section facing the permanent magnet section has multiple circumferentially arrayed filling holes that extend to the magnetic bearing position area. Each filling hole is filled with a metal core with a density higher than that of the mandrel section. Multiple circumferentially arrayed filling grooves are formed on the outer surface of the mandrel segment, extending from the permanent magnet shaft segment to the magnetic bearing location area. Each filling groove is filled with a metal strip with a density higher than that of the mandrel segment and matching the outer surface of the mandrel segment.

2. The high-speed motor rotor structure with optimized interference fit according to claim 1, characterized in that: The centrifugal deformation hole is filled with a thermal expansion material that completely seals it and has a higher coefficient of thermal expansion than the mandrel section.

3. The high-speed motor rotor structure with optimized interference fit according to claim 2, characterized in that: The mandrel section has multiple circumferentially arrayed heat dissipation holes on the surface of the magnetic bearing location area, which are oriented towards the centrifugal force deformation hole.

4. The high-speed motor rotor structure with optimized interference fit according to claim 3, characterized in that, All heat dissipation holes are close to the centrifugal force deformation holes but are not connected to them.

5. The high-speed motor rotor structure with optimized interference fit according to any one of claims 1-4, characterized in that, It also includes protective sleeves that are interference-fitted to the outside of the permanent magnet shaft section and the outside of the spindle sections at both ends.

6. The high-speed motor rotor structure with optimized interference fit according to claim 4, characterized in that, The centrifugal deformation hole is called centrifugal deformation hole one in the area where the protective sleeve is located, and centrifugal deformation hole two in the area where the magnetic bearing is located, wherein the diameter of centrifugal deformation hole two is greater than or equal to the diameter of centrifugal deformation hole one.

7. The high-speed motor rotor structure with optimized interference fit according to claim 1, characterized in that: The diameter of the centrifugal deformation hole is 0.3-0.4 times the minimum diameter of the mandrel section.

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