High-speed motor rotor structure for optimizing magnitude of interference

Abstract

The invention discloses a high-speed motor rotor structure for optimizing the magnitude of interference, which belongs to the technical field of motor rotors and comprises a permanent magnet shaft section located in the middle, core shaft sections concentrically connected to the left end and the right end of the permanent magnet shaft section and magnetic bearings assembled on the outer sides of the shaft ends of the core shaft sections in an interference mode. A centrifugal force deformation hole extending from the permanent magnet shaft section to the magnetic bearing position area is coaxially formed in the center of the core shaft section. The interference magnitude optimized high-speed motor rotor structure is used in a magnetic suspension motor, through the design of a centrifugal force deformation hole in the center of the mandrel section, part of centrifugal stress is released by using radial deformation of the hole during high-speed rotation, so that smaller initial interference magnitude is allowed without causing excessive attenuation of surface pressure, and meanwhile, structural strength and mass production adaptability are considered.

Description

Technical Field

[0001] The present invention relates to the technical field of motor rotors, and in particular to a high-speed motor rotor structure with optimized interference. Background Art

[0002] As the core power component of high-end equipment, the rotor of the magnetic levitation motor needs to maintain high stiffness, low vibration and stable interference fit under high-speed rotation (such as 1-5 rpm). The rotor of a traditional magnetic levitation motor is usually composed of a permanent magnet shaft segment, a core shaft segment and a magnetic bearing, in which the magnetic bearing and the core shaft segment are connected by an interference fit to transmit torque and constrain radial displacement. However, as the speed increases, the magnetic bearing assembly and the core shaft will produce radial expansion, and the stiffness of the magnetic bearing rotor assembly is small, and the radial deformation is greater, resulting in the attenuation of the surface pressure of the interference surface between the core shaft and the magnetic bearing. Figure 1 As shown ( Figure 1 For an un-drilled model: Equivalent stress and residual surface pressure values. As can be seen from the figure, when the interference is 0.14, the contact surface pressure is 0. A smaller interference does not meet the requirements. When the interference is 0.18, the equivalent stress is 390 MPa, exceeding the material yield limit and failing the strength requirements. The lower limit of the interference is 0.15, and the upper limit is 0.17, with a range of only two threads, which does not meet the requirement of mass production of four threads. Excessive attenuation of the surface pressure may cause fit failure, increased vibration, and even equipment damage.

[0003] Traditional solutions compensate for centrifugal relaxation by increasing the initial interference. However, due to limitations in material strength (excessive interference causes plastic deformation of the silicon steel sheets in the rotor assembly, affecting control accuracy) and machining accuracy (micron-level interference is difficult to stably control), there is an upper limit to the increase in interference, making it difficult to meet the demands of higher speeds (e.g., ≥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 a magnetic levitation motor. By designing a centrifugal force deformation hole in the center of the core shaft segment, 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 the rotor to underpress insufficiently at high speeds, while taking into account both structural strength and mass production adaptability.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A high-speed motor rotor structure with optimized interference fit includes a permanent magnet shaft section located in the middle, a core shaft section concentrically connected to the left and right ends of the permanent magnet shaft section, and a magnetic bearing interference-fitted on the outside of the shaft end of the core shaft section; a centrifugal force deformation hole extending from the permanent magnet shaft section to the magnetic bearing position area is coaxially provided at the center of the core shaft section, and the centrifugal stress distribution is adjusted by radial deformation of the centrifugal force deformation hole, thereby optimizing the interference fit performance.

[0006] By adopting the above solution, the high-speed motor rotor structure with optimized interference releases part of the centrifugal stress through the radial deformation of the centrifugal deformation hole. While ensuring that the surface pressure does not decay excessively, the initial interference is allowed to be reduced by 5-15%, solving the problem of insufficient rotor assembly 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 adapt to rotors with different speed requirements and has a certain degree of adaptability to mass production.

[0007] As a preferred embodiment of a high-speed motor rotor structure for optimizing interference, the diameter of the centrifugal deformation hole is 0.3-0.4 times the minimum diameter of the core shaft segment. This size range is optimized based on the centrifugal expansion characteristics of the material: smaller centrifugal deformation hole diameters (≤0.3 times) cannot effectively release stress; larger diameters (≥0.4 times) significantly reduce the core shaft segment stiffness, resulting in 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 during high-speed rotation of the core shaft segment (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 rotation radius, and E is the elastic modulus). This partially relieves centrifugal stress at the contact interface between the core shaft segment and the magnetic bearing, allowing the initial interference to be reduced by 5-15% (compared to traditional structures without deformation holes).

[0008] As a preferred embodiment of a high-speed motor rotor structure for optimizing interference fit, the inner wall of the centrifugal deformation hole is coated with a metal layer with a higher density than the core shaft segment, such as a high-density tungsten-based alloy (density 17-19 g / cm³) or lead alloy (11.3 g / cm³). This layer is denser than the core shaft segment made of alloy steel (density 7.9 g / cm³). The layer has a thickness of 1-3 mm and is bonded to the inner wall of the deformation hole via thermal spraying (such as plasma spraying) or electroplating (such as nickel electroplating). The bond strength is ≥50 MPa. During high-speed rotation, the centrifugal stress of the metal layer amplifies the radial deformation of the core shaft segment, thereby reducing excessive attenuation of the downward pressure at high speeds.

[0009] As a preferred embodiment of a high-speed motor rotor structure with optimized interference, the centrifugal deformation hole is filled with a thermal expansion material that completely blocks it and has a higher thermal expansion coefficient than the core shaft segment. The thermal expansion material is a high-expansion alloy steel (such as FeNi3Mn7 or Mn72Cr18Ni10 alloy), and the thermal expansion coefficient of the core shaft segment is 11×10⁻ 6 / ℃, the thermal expansion coefficient of FeNi3Mn7 or Mn72Cr18Ni10 alloy 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 operating temperature) and fully squeezes the centrifugal deformation hole outward. Under the action of centrifugal force, the radial deformation of the core shaft segment increases, further reducing excessive attenuation of surface pressure.

[0010] As a preferred implementation method of a high-speed motor rotor structure with optimized interference fit, a plurality of heat dissipation holes distributed in a circumferential array and facing the centrifugal deformation holes are opened on the surface of the core shaft segment in the magnetic bearing position area. The number of heat dissipation holes is 6-10, the diameter is 0.5-2 mm, and the depth is 1 / 5-1 / 4 of the radius of the core shaft segment; all the heat dissipation holes are close to the centrifugal deformation holes but are not connected to the centrifugal deformation holes. Because the heat dissipation holes face the deformation holes but are not connected, the airflow can be guided to flow toward the centrifugal deformation holes, thereby enhancing the heat exchange efficiency and promoting the thermal expansion material to be fully heated.

[0011] As a preferred embodiment of a high-speed motor rotor structure that optimizes interference fit, the core shaft segment has multiple circumferentially arranged filling holes on the end surface facing the permanent magnet shaft segment, extending all the way to the magnetic bearing area. The number of filling holes ranges from 2 to 6, with a diameter of 1 to 3 mm. Each filling hole is filled and fixed with a metal core with a higher density than the core shaft segment. The metal core is made of a high-density tungsten-based alloy (density 17-19 g / cm³) or a lead alloy (11.3 g / cm³), and is secured to the filling hole by interference fit (interference fit of 0.01 to 0.05 mm). During high-speed rotation, the centrifugal stress of the metal core amplifies the radial deformation of the core shaft segment, releasing some of the centrifugal stress, thereby further attenuating excessive surface pressure.

[0012] As a preferred embodiment of a high-speed motor rotor structure with optimized interference fit, the outer surface of the core segment is provided with a plurality of circumferentially arranged filling slots extending from the permanent magnet shaft segment to the magnetic bearing area. The number of filling slots ranges from 2 to 6, and the shape of the filling slots is rectangular. Each filling slot is filled with a metal strip with a higher density than the core segment and matching the outer surface of the core segment. The metal strip is made of the same material as the metal core and is fixed to the filling slot through embedded fixing (such as gluing) with a fit degree of ≥95%. During high-speed rotation, the centrifugal stress of the metal strip amplifies the radial deformation of the core segment, releasing some of the centrifugal stress, thereby further attenuating excessive surface pressure.

[0013] As a preferred embodiment of a high-speed motor rotor structure for optimizing interference fit, in order to improve the overall stiffness and corrosion resistance of the rotor, it also includes a protective sleeve that is interference-fitted on the outside of the permanent magnet shaft segment and the outside of the core shaft segments at its left and right ends. The material of the protective sleeve is a high-strength alloy, and the interference fit with the permanent magnet shaft segment and the core shaft segment is 0.02-0.1mm, and the axial length covers 60-70% of the total length of the permanent magnet shaft segment and the core shaft segment.

[0014] As a preferred embodiment of a high-speed motor rotor structure for optimizing interference fit, the centrifugal deformation hole is designated as Centrifugal Deformation Hole 1 within the protective sleeve area, and as Centrifugal Deformation Hole 2 within the magnetic bearing area. The diameter of Centrifugal Deformation Hole 2 is greater than or equal to the diameter of Centrifugal Deformation Hole 1, with the diameter difference being 5-20% of that of Centrifugal Deformation Hole 1. This zoned design is designed because the interference fit between the magnetic bearing and the core shaft segment is sensitive to deformation (requiring precise control of surface pressure), while the core shaft segment covered by the protective sleeve has greater rigidity, allowing for greater deformation.

[0015] The beneficial effects produced by the present invention are: 1. Optimize the interference range: The radial deformation of the centrifugal deformation hole releases some centrifugal stress, while ensuring that the surface pressure does not decay excessively. The initial interference is allowed to be reduced by 5-15%, solving the problem of insufficient rotor assembly strength caused by excessive interference. It is suitable for magnetic levitation motors with higher speeds (≥40,000 rpm).

[0016] 2. Further reduce surface pressure attenuation: By adding metal layers, thermal expansion materials, metal cores or metal strips, the surface pressure attenuation under high-speed rotation is reduced.

[0017] 3. Enhanced structural reliability: The additional design of heat dissipation holes, because the heat dissipation holes are facing the deformation holes but not connected, can guide the airflow to flow toward the centrifugal deformation holes, enhance the heat exchange efficiency, and promote the thermal expansion material to be fully and evenly heated.

[0018] 4. Convenient for mass production: This solution can reduce the lower limit of the interference fit and can meet the upper limit-lower limit>4 wires under extreme conditions without the need for grinding and installation, so as to meet mass production requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 The equivalent stress diagram of the interference between the traditional core shaft and the magnetic bearing in the background technology; Figure 2 This is a transverse cross-sectional view of the high-speed motor rotor structure with optimized interference in Example 1; Figure 3 for Figure 2 Schematic diagram of part of the structure; Figure 4 A longitudinal cross-sectional view of the high-speed motor rotor structure with optimized interference in Example 1; Figure 5 This is an equivalent stress diagram of the interference between the traditional core shaft and the magnetic bearing in Example 1; Figure 6 A longitudinal cross-sectional view of the high-speed motor rotor structure with optimized interference in Example 2; Figure 7 A longitudinal cross-sectional view of the high-speed motor rotor structure with optimized interference in Example 3; Figure 8 A longitudinal cross-sectional view of the high-speed motor rotor structure with optimized interference in Example 4; Figure 9 A longitudinal cross-sectional view of the high-speed motor rotor structure with optimized interference in Example 5; Markings in the figure: 1-magnetic bearing; 2-core shaft segment; 2-1 centrifugal force deformation hole; 3-protective sleeve; 4-permanent magnetic shaft segment; 5-metal layer; 6-thermal expansion material; 7-heat dissipation hole; 8-metal core; 9-metal strip. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] Example 1, as Figures 2 to 5 As shown, a high-speed motor rotor structure with optimized interference fit is provided, which is used in a magnetic levitation motor. The structure specifically includes a permanent magnet shaft segment 4 (samarium cobalt) located in the middle, a core shaft segment 2 (alloy steel) concentrically connected to the left and right ends of the permanent magnet shaft segment 4, a magnetic bearing 1 (silicon steel sheet) interference-fitted on the outside of the axial end of the core shaft segment 2, and a protective sleeve 3 interference-fitted on the outside of the permanent magnet shaft segment 4 and the outside of the shaft body of the core shaft segment 2 on both sides. The material of the protective sleeve 3 is a high-strength alloy, and of course it can also be a carbon fiber composite material (density 1.8g / cm³). The interference fit with the permanent magnet shaft segment 4 and the core shaft segment 2 is 0.05mm, and the axial length covers 65% of the total length of the permanent magnet shaft segment 4 and the core shaft segment 2, and this value can be in the range of 60-70%; the center of the core shaft segment 2 is coaxially provided with a centrifugal force deformation hole extending from the permanent magnet shaft segment 4 to the position area of ​​the magnetic bearing 1, and the interference fit performance is optimized by radial deformation of the centrifugal force deformation hole. The high-speed motor rotor structure with optimized interference reduces the surface pressure attenuation at high speeds through the radial deformation of the centrifugal deformation hole, allowing the initial interference to be reduced by 5-15%, such as Figure 5 As shown ( Figure 5For the opening model: the lower limit of interference is 0.12, the upper limit of interference is 0.16, the surface pressure is > 0 when the lower limit of interference is exceeded, the material yield limit is not exceeded when the upper limit of interference is exceeded, and the mass production requirements of 4 wires are met). This solves the lower limit problem 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 deformation hole, it can adapt to rotors with different speed requirements and has a certain degree of mass production adaptability.

[0023] like Figure 4 As shown, the centrifugal deformation hole is 0.3-0.4 times the minimum diameter of the core shaft 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) significantly reduces the stiffness of the core shaft segment 2, resulting in a decrease in the critical speed of the rotor. The presence of the deformation hole causes the area around the hole to expand radially outward due to centrifugal force when the core shaft 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 rotation radius, and E is the elastic modulus). This partially releases the centrifugal stress at the contact interface between the core shaft segment 2 and the magnetic bearing 1, allowing the initial interference fit to be reduced by 5-15% (compared to a traditional structure without a deformation hole).

[0024] like Figures 2 to 3 As shown, the centrifugal deformation hole in the area where the protective sleeve 3 is located is centrifugal deformation hole 1, and the centrifugal deformation hole in the area where the magnetic bearing 1 is located is centrifugal deformation hole 2. The diameter of centrifugal deformation hole 2 is equal to the diameter of centrifugal deformation hole 1. Of course, the diameter of centrifugal deformation hole 2 can also be larger than the diameter of centrifugal deformation hole 1, with the diameter difference being 5-20% of that of centrifugal deformation hole 1. The reason for the zoned design is that the interference fit area between the magnetic bearing 1 and the core shaft segment 2 is sensitive to deformation (requiring precise control of surface pressure), while the area of ​​the core shaft segment 2 covered by the protective sleeve 3 has higher rigidity and allows for greater deformation.

[0025] Example 2, as Figure 6 As shown, the only difference between this embodiment and the first embodiment is that, based on the first embodiment, the inner wall of the centrifugal deformation hole is covered with a metal layer 5 having a higher density than the core shaft segment 2. This metal layer 5 is made of a high-density tungsten-based alloy (density 17-19 g / cm³), or alternatively, a lead alloy (11.3 g / cm³), which has a higher density than the core shaft segment 2 made of stainless steel (density 7.9 g / cm³). It has a thickness of 1-3 mm and is bonded to the inner wall of the deformation hole via a thermal spraying (plasma spraying) process. Alternatively, electroplating (e.g., nickel electroplating) can be used, achieving a bonding strength of ≥50 MPa. During high-speed rotation, the centrifugal stress of the metal layer 5 amplifies the radial deformation of the core shaft segment 2, releasing some of the centrifugal stress, thereby further attenuating the excessive surface pressure.

[0026] Example 3, as Figure 7 As shown, the difference between this embodiment and the first embodiment is that, on the basis of the first embodiment, the centrifugal deformation hole is filled with a thermal expansion material 6 that completely blocks it and has a higher thermal expansion coefficient than the core shaft segment 2. The thermal expansion material 6 is a high expansion alloy steel (such as FeNi3Mn7 or Mn72Cr18Ni10, etc.), and the core shaft segment 2 is an alloy steel with a thermal expansion coefficient of 11×10⁻ 6 / ℃, the thermal expansion coefficient of FeNi3Mn7 or Mn72Cr18Ni10 is 21×10⁻ 6 The function of the thermal expansion material 6 is that after thermal expansion (from room temperature to working temperature), the thermal expansion material 6 fully squeezes the centrifugal deformation hole, which will expand the radial deformation of the core shaft segment 2, thereby reducing excessive attenuation of surface pressure.

[0027] Continue as Figure 7 As shown, a plurality of heat dissipation holes 7 distributed in a circumferential array and facing the centrifugal deformation holes are opened on the surface of the core shaft segment 2 in the position area of ​​the magnetic bearing 1. The number of heat dissipation holes 7 is 6, and the number can be in the range of 6-10. The depth is 1 / 5 of the radius of the core shaft segment 2, and the depth can be in the range of 1 / 5-1 / 4; all the heat dissipation holes 7 are close to the centrifugal deformation holes but are not connected to the centrifugal deformation holes. Because the heat dissipation holes 7 face the deformation holes but are not connected, the airflow can be guided to flow toward the centrifugal deformation holes, thereby enhancing the heat exchange efficiency and promoting the thermal expansion material 6 to be fully heated.

[0028] Example 4, as Figure 8 As shown, the only difference between this embodiment and the first embodiment is that, based on the first embodiment, a plurality of filling holes distributed in a circumferential array and extending all the way to the position area of ​​the magnetic bearing 1 are opened on the end face of the core shaft segment 2 facing the permanent magnetic shaft segment 4. The number of filling holes is 6, and the number can be within the range of 2-6. Each filling hole is filled and fixed with a metal core 8 having a density higher than that of the core shaft segment 2. The material of the metal core 8 is a high-density tungsten-based alloy (density 17-19g / cm³), and of course it can also be a lead alloy (11.3g / cm³). It is fixed to the filling hole by interference fit (interference amount 0.03mm). During high-speed rotation, the centrifugal stress of the metal core 8 will expand the radial deformation of the core shaft segment 2, releasing part of the centrifugal stress, thereby further attenuating the excessive surface pressure.

[0029] Example 5, as Figure 9As shown, the only difference between this embodiment and the first embodiment is that, based on the first embodiment, a plurality of filling slots distributed in a circumferential array and extending from the permanent magnet shaft segment 4 to the position area of ​​the magnetic bearing 1 are provided on the outer surface of the core shaft segment 2. The number of filling slots is 4, and the number can be in the range of 2-6. The filling slots are rectangular in shape, and each filling slot is filled and fixed with a metal strip 9 having a higher density than the core shaft segment 2 and matching the outer surface of the core shaft 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 slot by embedded fixation (gluing), with a fit degree of ≥95%. During high-speed rotation, the centrifugal stress of the metal strip 9 will amplify the radial deformation of the core shaft segment 2, releasing part of the centrifugal stress, thereby further attenuating the excessive surface pressure.

[0030] The above are only 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 in the scope of protection of the present invention.

Claims

1. A high-speed motor rotor structure with optimized interference fit, comprising a central permanent magnet shaft segment, core shaft segments concentrically connected to the left and right ends of the permanent magnet shaft segment, and magnetic bearings interference-fitted on the outer sides of the core shaft segments. Its characteristics are: The center of the core shaft segment is coaxially provided with a centrifugal force deformation hole extending from the permanent magnetic shaft segment to the magnetic bearing position area.

2. The high-speed motor rotor structure with optimized interference according to claim 1, characterized in that: The inner wall of the centrifugal deformation hole is covered with a metal layer having a density higher than that of the core shaft segment.

3. The high-speed motor rotor structure with optimized interference according to claim 1, characterized in that: The centrifugal deformation hole is filled with a thermal expansion material that completely blocks the hole and has a higher thermal expansion coefficient than the core shaft segment.

4. The high-speed motor rotor structure with optimized interference according to claim 3, characterized in that: The core shaft segment is provided with a plurality of heat dissipation holes on the surface of the magnetic bearing position area, which are distributed in a circumferential array and face the centrifugal force deformation hole.

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

6. The high-speed motor rotor structure with optimized interference according to claim 1, characterized in that: The end surface of the core shaft segment facing the permanent magnet shaft segment is provided with a plurality of filling holes distributed in a circumferential array and extending all the way to the magnetic bearing position area. Each filling hole is filled and fixed with a metal core having a higher density than that of the core shaft segment.

7. The high-speed motor rotor structure with optimized interference according to claim 1, characterized in that: The outer surface of the core shaft segment is provided with a plurality of filling grooves distributed in a circumferential array and extending from the permanent magnet shaft segment to the magnetic bearing position area, and each filling groove is filled with a metal strip having a higher density than the core shaft segment and matching the outer surface of the core shaft segment.

8. The high-speed motor rotor structure with optimized interference according to any one of claims 1 to 7, characterized in that: It also includes a protective sleeve which is interference fitted on the outer side of the permanent magnet shaft segment and the outer side of the shaft body of the core shaft segments at its left and right ends.

9. The high-speed motor rotor structure with optimized interference according to claim 8, characterized in that: The centrifugal force deformation hole is centrifugal force deformation hole one in the area where the protective cover is located, and the centrifugal force deformation hole is centrifugal force deformation hole two in the area where the magnetic bearing is located, wherein the diameter of the centrifugal force deformation hole two is greater than or equal to the diameter of the centrifugal force deformation hole one.

10. The high-speed motor rotor structure with optimized interference 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 core shaft section.

Images