Assembling method of micro motor and micro motor structure thereof

Abstract

The invention relates to the technical field of micro motor production, in particular to a micro motor assembly method and a micro motor structure thereof, and the method comprises the following steps: S1, pressing a stator assembly into a housing at a preset phase angle, and enabling a wedge-shaped projection and an annular clamping groove to generate axial component force for locking; s2, after the bearing seat is cooled through liquid nitrogen, the rotor shaft is pressed, and interference fit is formed after normal temperature is recovered; s3, axial compression is applied to the shape memory alloy ring when the end cover is installed, and heating is conducted till radial expansion is triggered; and S4, the motor is operated at the rated rotating speed, and the buffer pad at the bottom of the bearing seat generates plastic deformation through centrifugal force so that the buffer pad can be attached to the interior of the shell. Self-fastening of the micro motor in a vibration environment is achieved through the synergistic effect of geometric constraint and material characteristics, it is guaranteed that the structure of the micro motor can be kept stable for a long time under long-term vibration, the micro motor is not prone to loosening, and the structural stability is high.

Description

Technical Field

[0001] The present invention relates to the technical field of micro motor production, and in particular to a micro motor assembly method and a micro motor structure. Background Art

[0002] Micromotors, as core components of precision drive systems, are widely used in aerospace, medical devices, and microrobotics. As applications expand into high-frequency vibration and high-impact environments, traditional micromotors are susceptible to problems such as stator assembly displacement, loose bearing fits, and end cap seal failure under long-term vibration loads, leading to performance degradation and even structural damage. Existing technologies typically use mechanical fastening methods such as interference fits, elastic clips, or threaded fastening to secure components. However, these rigid connections are prone to stress concentration and fatigue microcracks under the accumulation of alternating vibration energy, making them difficult to maintain long-term stability. For example, conventional stator-to-housing assembly often utilizes a combination of equal-depth grooves and protrusions. This provides a single axial locking force and cannot adapt to dynamic load variations under vibration conditions, leading to accumulated phase angle shifts. The assembly between the bearing seat and the rotor shaft is also prone to cold brittleness or uneven interference fit. Furthermore, existing cushioning materials lack sufficient damping properties and cannot effectively dissipate high-frequency vibration energy through plastic deformation, causing micro-displacement resonance in the bearing assembly and compromising the stability of the assembled motor. Summary of the Invention

[0003] In response to the problems of the prior art, the present invention provides a micromotor assembly method and a micromotor structure thereof. The design is ingenious. Under the assembly and connection cooperation of the stator assembly, housing, bearing seat, rotor shaft and end cover, the self-tightening of the micromotor in a vibration environment is achieved through the synergistic effect of geometric constraints and material properties. The phase assembly of the annular groove with gradually varying depth and the wedge-shaped stator is utilized. Combined with the vibration energy dissipation compensated by the thermal deformation of the shape memory alloy ring during the assembly of the end cover, it is ensured that the structure of the micromotor can remain stable for a long time under long-term vibration, is not easy to loosen, and has strong structural stability.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for assembling a micro motor, comprising the following steps: Step S1, pressing a stator assembly into a housing at a preset phase angle so that a wedge-shaped protrusion and an annular groove generate an axial force component for locking;

[0006] Step S2: Cool the bearing seat with liquid nitrogen and then press-fit the rotor shaft, and form an interference fit after returning to room temperature;

[0007] Step S3: applying axial compression to the shape memory alloy ring when installing the end cover, and heating it until it triggers radial expansion;

[0008] Step S4: Run the motor at the rated speed, and use centrifugal force to plastically deform the buffer pad at the bottom of the bearing seat so that it fits into the housing.

[0009] In step S2, the bearing seat is cooled to -196°C by liquid nitrogen, and the rotor shaft is press-fitted at a speed of 0.5 mm / s and a press-fitting pressure of 50 MPa. After returning to room temperature, an interference fit is formed between the bearing seat and the rotor shaft.

[0010] Wherein, in step S2, the tapered bearing seat is completely immersed in liquid nitrogen, and the cooling rate is controlled according to a non-uniform gradient; the method of controlling the non-uniform gradient is:

[0011] When cooling the conical surface area of the tapered bearing seat, the cooling rate is 50°C / min; when cooling the bottom area of the tapered bearing seat, the cooling rate is 30°C / min; the cooling time t is calculated based on the workpiece mass, formula: t = 0.05m 1.2 , where t is the cooling time and m is the workpiece mass.

[0012] Wherein, in the step S3, when installing the end cover, axial compression is applied to the shape memory alloy ring and heated to 80-100° C. to trigger radial expansion.

[0013] Wherein, in the step S3, when the end cover is installed, axial compression is applied to the shape memory alloy ring, and when cooled to 20° C., the shape memory alloy ring radially shrinks by 0.12%.

[0014] Wherein, in the step S2, the bearing seat is cooled by liquid nitrogen and then subjected to low-temperature tempering at 150° C. for 2 h.

[0015] Wherein, in said step S2, when the bearing seat is cooled by liquid nitrogen, the bearing seat is positioned on a turntable, and the turntable drives the bearing seat to rotate at a constant speed in the liquid nitrogen.

[0016] The present invention also provides a micro-motor structure formed according to the assembly method of the micro-motor, which includes a shell, a stator assembly, a rotor shaft, a bearing seat and an end cover. The inner wall of the shell is provided with an annular groove, the depth of the annular groove is gradually set along the circumferential direction, the outer edge of the stator assembly is provided with a wedge-shaped protrusion that cooperates with the annular groove, the outer surface of the wedge-shaped protrusion is covered with a viscoelastic damping layer, the rotor shaft is pressed into the bearing seat, the bearing seat is conical, and the bottom of the bearing seat is provided with a corrugated buffer pad; the upper end of the shell is provided with an opening, and the outer periphery of the lower end of the end cover is embedded with a shape memory alloy ring, the end cover is installed at the upper end of the shell and is used to close the opening. When the end cover is installed at the upper end of the shell, the end cover is heated so that the shape memory alloy ring generates a radial preload force after heat treatment and abuts and locks with the inner wall of the shell.

[0017] Wherein, the viscoelastic damping layer is a silica gel-graphene composite material with a thickness of 0.1-0.3 mm and a loss factor ≥ 0.5.

[0018] The inner wall of the shell is also provided with a plurality of elastic buckles at equal intervals. The elastic buckles are arranged in a cantilever beam structure, and the ends of the elastic buckles are provided with hemispherical protrusions.

[0019] Beneficial effects of the present invention:

[0020] The present invention is ingeniously designed. Through the assembly and connection of the stator assembly, housing, bearing seat, rotor shaft and end cover, the self-tightening of the micromotor in a vibration environment is achieved through the synergistic effect of geometric constraints and material properties. The phase assembly of the annular groove with gradually varying depth and the wedge-shaped stator is combined with the vibration energy dissipation compensated by the thermal deformation of the shape memory alloy ring during the assembly of the end cover. This ensures that the structure of the micromotor can remain stable for a long time under long-term vibration, is not easy to loosen, and has strong structural stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a flow chart of an assembly method of a micro motor of the present invention.

[0022] Figure 2 This is a structural exploded view of a micro motor structure of the present invention.

[0023] exist Figures 1 to 2 Reference numerals in the figures include:

[0024] 1. Housing; 2. Stator assembly; 3. Rotor shaft; 4. Bearing seat; 5. End cover; 6. Annular groove; 7. Wedge-shaped protrusion; 8. Corrugated buffer pad; 9. Shape memory alloy ring; 10. Elastic buckle; 11. Hemispherical protrusion. DETAILED DESCRIPTION

[0025] In order to facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the embodiments and the accompanying drawings. The contents mentioned in the embodiments are not intended to limit the present invention. The present invention will be described in detail below with reference to the accompanying drawings.

[0026] Example 1

[0027] The first embodiment of the present application provides a method for assembling a micro motor. Figure 1As shown, it includes the following steps: step S1, pressing the stator assembly into the housing at a preset phase angle, so that the wedge-shaped protrusion and the annular groove generate an axial force lock (the axial force is 15N), and the depth of the annular groove is set gradually; step S2, after cooling the bearing seat with liquid nitrogen, press-fitting the rotor shaft, and forming an interference fit after returning to room temperature; step S3, applying axial compression to the shape memory alloy ring when installing the end cover, and heating it to trigger radial expansion; step S4, running the motor at rated speed for 30 minutes, using centrifugal force to plastically deform the buffer pad at the bottom of the bearing seat so that it fits into the housing; wherein, the buffer pad is a corrugated buffer pad. Specifically, the present invention is ingeniously designed. Through the assembly and connection of the stator assembly, housing, bearing seat, rotor shaft and end cover, the self-tightening of the micromotor in a vibration environment is achieved through the synergistic effect of geometric constraints and material properties. The phase assembly of the annular groove with gradually varying depth and the wedge-shaped stator is combined with the vibration energy dissipation compensated by the thermal deformation of the shape memory alloy ring during the assembly of the end cover. This ensures that the structure of the micromotor can remain stable for a long time under long-term vibration, is not easy to loosen, and has strong structural stability.

[0028] In the first embodiment of the present application, in the step S2, the bearing seat is cooled by liquid nitrogen to -196°C, and the rotor shaft is pressed at a speed of 0.5mm / s and a pressing pressure of 50Mpa. After returning to normal temperature, an interference fit is formed between the bearing seat and the rotor shaft. Wherein, in the step S2, when the bearing seat is cooled by liquid nitrogen, the bearing seat is positioned on the turntable, and the turntable drives the bearing seat to rotate at a uniform speed in the liquid nitrogen; wherein, the uniform rotation can ensure uniform contact between the liquid nitrogen and the bearing seat, and ensure that the temperature difference between each surface position of the bearing seat is less than 5°C; preferably, an annular nozzle is provided in the liquid nitrogen-cooled cooling cavity, and the inner side wall of the annular nozzle is provided with a plurality of spray holes at equal intervals; further, in the liquid nitrogen-cooled workstation cavity, gas-liquid two-phase nitrogen is sprayed into the cooling cavity through the spray holes of the annular nozzle, and the spray pressure is controlled to be 0.15MPa to reduce the risk of cold shock cracks.

[0029] In the first embodiment of the present application, the bearing seat is conical and made of stainless steel or other alloys. In step S2, the conical bearing seat is completely immersed in liquid nitrogen, and the cooling rate is controlled according to a non-uniform gradient. The non-uniform gradient control method is as follows: when cooling the conical surface area of the conical bearing seat, the cooling rate is 50°C / min. Under this setting, the material shrinkage efficiency is enhanced.

[0030] When cooling the bottom area of the tapered bearing seat, the cooling rate is 30°C / min. Under this setting, stress concentration at the bottom of the tapered bearing seat is reduced, so that the bottom of the bearing seat and the bottom of the inner wall of the housing are more closely fitted during press-fitting.

[0031] When cooling the bearing seat, the cooling time t is calculated based on the workpiece mass, formula: t = 0.05m 1.2 , where t is the cooling time (min) and m is the mass of the workpiece (kg).

[0032] In the first embodiment of the present application, when the rotor shaft is pressed into the bearing seat, a staged press-fitting operation can be adopted. After the bearing seat is cooled, the bearing seat is pressed into the rotor shaft at a staged speed of 0.5 mm / s, specifically in three stages:

[0033] Initial stage (when the press-fit stroke of the rotor shaft is 0-0.2mm): speed 0.3mm / s. Under this setting, sudden shrinkage of the bearing seat can be avoided, achieving a slow adaptation effect;

[0034] Main pressing stage (when the rotor shaft press-fitting stroke is 0.2-0.45mm): speed 0.6mm / s. Under this setting, it is helpful to ensure the interference between the rotor shaft and the bearing seat;

[0035] Final pressing stage (when the press-fitting stroke of the rotor shaft is 0.45-0.5 mm): speed 0.2 mm / s. Under this setting, it is beneficial to eliminate the residual stress between the rotor shaft and the bearing seat and reduce the stress concentration factor to 1.8.

[0036] In the first embodiment of the present application, the above-mentioned graded press-fitting operation is used to ensure that the rotor shaft and the bearing seat are press-fitted reliably and stably, and that sudden shrinkage changes are not easily produced, thereby ensuring the interference fit between the rotor shaft and the bearing seat and eliminating residual stress. This improves the press-fitting effect between the rotor shaft and the bearing seat. Of course, in order to detect whether there is an interference fit between the rotor shaft and the bearing seat, a temperature recovery monitoring system (infrared temperature monitoring and sensor monitoring, etc.) is used to monitor the situation between the rotor shaft and the bearing seat. After the temperature is restored to normal, an interference fit (interference amount -0.03mm) is formed between the rotor shaft and the bearing seat. The axial displacement between the rotor shaft and the bearing seat is monitored in real time (when the axial displacement is <±1.2μm), and it can be determined that the press-fitting effect between the rotor shaft and the bearing seat is reliable.

[0037] In the embodiment of the present application, in the step S3, when the end cover is installed, axial compression is applied to the shape memory alloy ring, and radial expansion is triggered by heating to 80-100°C. In the step S3, when the end cover is installed, axial compression is applied to the shape memory alloy ring, and when cooled to 20°C, the shape memory alloy ring radially shrinks by 0.12%; wherein the shape memory alloy ring is a Ni-Ti-Cu-V alloy ring; axial compression is applied to the Ni-Ti-Cu-V alloy ring, and radial expansion (0.25% strain) is triggered when heated to 90°C; dual-modal compensation: radial contraction of 0.12% when cooled to -20°C, achieving temperature-adaptive preload; preload fluctuation <5% (-40 to 120°C working conditions); the embodiment of the present application introduces a shape memory alloy ring (Ni-Ti-Cu system), which triggers radial expansion (0.25% strain) through heat treatment, compensates for axial wear in real time, and the preload fluctuation is <5%.

[0038] In the embodiment of the present application, the material of the buffer pad is a silicone-carbon nanotube composite material, which forms a microscopic wrinkle structure after plastic deformation to enhance the damping performance.

[0039] Example 2

[0040] In the second embodiment of the present application, in step S2, the bearing seat is cooled by liquid nitrogen and then subjected to low-temperature tempering; the process steps are as follows:

[0041] Temperature recovery control:

[0042] Natural temperature return: After liquid nitrogen cooling is completed, the bearing seat needs to be taken out of the deep freezer (cooling chamber) and naturally return to room temperature (25°C) in the air. It is prohibited to temper directly before reaching room temperature to avoid cracking caused by excessive temperature difference; surface treatment: wipe off the frost on the surface and immediately spray anti-rust oil (such as phosphate anti-rust agent) to prevent oxidation;

[0043] Tempering parameter setting:

[0044] Temperature range: the tempering temperature is controlled at 160-180℃ (for high carbon alloy steels such as bearing steel); if the material is stainless steel or molybdenum / chromium alloy, the temperature can be appropriately lowered to 150-170℃;

[0045] Holding time: a single piece of bearing seat should be kept warm for 2 hours to ensure that residual stress is fully released; in batch processing, the holding time will be extended by 0.5 hours for every 50% increase in the furnace load (for example, the holding time will be extended to 3 hours when the furnace load is 200%).

[0046] Tempering operation process:

[0047] Preheat the equipment and tempering furnace to the target temperature (±5°C) to avoid uneven heating of the workpiece;

[0048] Step heating: a two-stage heating method is used. The first stage is to heat up to 100℃ at a rate of 5℃ / min; the second stage is to heat up to the target temperature at a rate of 3℃ / min.

[0049] Gas control: nitrogen is introduced into the tempering furnace for protection, and the oxygen content is ≤0.5% to prevent surface oxidation and decarburization;

[0050] Cooling method: After tempering is completed, cool it down to below 80℃ with the furnace before taking it out to avoid secondary stress caused by rapid cooling;

[0051] Performance testing, testing surface hardness (HV 700-750) and retained austenite content (≤5%) to ensure structural stability.

[0052] After the above tempering process, after many experiments, the following technical comparison is obtained:

[0053] parameter Traditional tempering process This application process optimization plan Heating rate Single rate (5℃ / min) Two-stage temperature control (5→3℃ / min) Oxygen content control Not mandatory (high oxidation risk) ≤0.5% (nitrogen protection) Retained austenite 8～12％ ≤5％ Batch processing efficiency 3 hours to 100% loading 200% loading in just 3 hours

[0054] The tempering process of the present application, through the synergistic effect of step temperature control, nitrogen protection and precise holding time, can eliminate more than 90% of the residual stress caused by liquid nitrogen cooling, while increasing the toughness of the material by 15 to 20%.

[0055] In the embodiment of the present application, during the tempering process of the bearing seat, the core purpose of introducing nitrogen into the tempering furnace is to control the gas environment in the furnace and prevent harmful reactions such as oxidation and decarburization of the material at high temperatures. The specific functions include: preventing surface oxidation, inhibiting decarburization reactions, controlling temperature uniformity, and providing safety protection. The specific description is as follows:

[0056] Isolate oxygen. Nitrogen acts as an inert gas, which can reduce the oxygen content in the furnace to ≤0.5%, blocking direct contact between the metal surface and oxygen and preventing the formation of oxide scale (Fe3O4, Fe2O3, etc.). Oxide scale will increase surface roughness (Ra value increases by 0.2-0.5μm), affecting the assembly accuracy of the bearing seat.

[0057] Maintain surface smoothness. In an oxygen-free environment, the surface of the bearing seat maintains the original metal color, reducing the difficulty of subsequent processing (such as grinding and plating).

[0058] Carbon element protection: In an oxygen-containing environment, high temperature will cause the carbon element in the steel to combine with oxygen to generate CO or CO2 (decarburization reaction), resulting in a decrease in the surface carbon content; the decarburization layer depth can reach 0.05-0.1mm, resulting in a decrease in surface hardness (HV reduction of 50-100) and a shortened fatigue life;

[0059] Maintaining material properties, under nitrogen protection, the carbon content on the bearing seat surface is stable, ensuring the integrity of the hardened layer, and the wear resistance and tensile strength meet the design requirements.

[0060] The uniform temperature medium, nitrogen, circulates in the furnace (flow rate 0.5-1.0m / s), promoting uniform heat distribution and reducing local temperature differences (within ±5°C) to avoid uneven tempering (such as local over-tempering or under-tempering) caused by temperature gradients.

[0061] Reduce thermal stress. The uniform temperature field can reduce the residual stress inside the workpiece and prevent deformation after tempering (such as ovality deviation <0.01mm);

[0062] Inhibit the generation of harmful gases, prevent lubricating oil residues from cracking at high temperatures to produce corrosive gases such as CO and H2S, and protect the furnace and sensors;

[0063] Safety protection: Nitrogen can replace combustible gases (such as hydrogen) in the furnace to reduce the risk of explosion.

[0064] The comparison between the nitrogen filling process in the present application embodiment and the traditional process is shown in the following table:

[0065] parameter No nitrogen protection (air environment) Nitrogen protection process (this application) Surface oxide layer 5~10μm <1μm Decarburization layer depth 0.08~0.12mm Not detected Hardness uniformity HV fluctuation ±50 HV fluctuation ±10 Furnace temperature uniformity ±15℃ ±5℃

[0066] From this, it can be seen that the introduction of nitrogen in this application is a key link in controlling material properties in the tempering process: by isolating oxygen, oxidation and decarburization are avoided, and surface hardness and wear resistance are maintained; uniform temperature is achieved through gas circulation, thermal stress is reduced, and dimensional stability is guaranteed; in precision bearing manufacturing, nitrogen protection can increase the life of the workpiece by 20% to 30%.

[0067] Example 3

[0068] In the third embodiment of the present application, Figure 2 As shown, a micro motor structure is also provided, which includes a shell, a stator assembly, a rotor shaft, a bearing seat and an end cover, the inner wall of the shell is provided with an annular groove, the depth of the annular groove is gradually set along the circumferential direction, the outer edge of the stator assembly is provided with a wedge-shaped protrusion that cooperates with the annular groove, the outer surface of the wedge-shaped protrusion is covered with a viscoelastic damping layer, the rotor shaft is pressed into the bearing seat, the bearing seat is conical, and the bottom of the bearing seat is provided with a corrugated buffer pad; the upper end of the shell is provided with an opening, and the outer periphery of the lower end of the end cover is embedded with a shape memory alloy ring, the end cover is installed at the upper end of the shell and is used to close the opening, when the end cover is installed at the upper end of the shell, the end cover is heated so that the shape memory alloy ring generates a radial preload force after the heat treatment and abuts and locks with the inner wall of the shell. Specifically, multiple experiments have shown that the micromotor structure formed according to the micromotor assembly method has a screw loosening rate reduced by 92% under 2000Hz vibration, an axial displacement of less than 3μm, and extremely strong structural stability, and is not easy to loosen.

[0069] The depth of the annular groove varies in a gradient of 0.05 mm / °. During assembly, the stator assembly needs to be rotated to a specific phase angle to be fully embedded. The gradient calculation formula of the annular groove is: Δh = 0.05 × θ (θ is the phase angle). For example, when the stator assembly is rotated to a phase angle θ = 30° (groove depth Δh = 1.5 mm), it is embedded in the housing. When the stator assembly and the housing are assembled, a laser positioning sensor (industrial camera) can be used to calibrate the phase. The angle of the wedge-shaped protrusion (forming a self-locking angle with the inner wall of the annular groove) is 12°. The locking position between the wedge-shaped protrusion and the annular groove is: when the stator is rotated to θ = 30°, the protrusion is fully embedded in the deepest area of the groove, generating an axial preload of 15 N. A continuous axial component force (about 15 N) is generated between the two, effectively offsetting the separation trend caused by vibration. No additional locking parts are required, and assembly efficiency is improved by 40%.

[0070] In an embodiment of the present application, the viscoelastic damping layer is a silicone-graphene composite material with a thickness of 0.1-0.3 mm and a loss factor ≥ 0.5; further, the silicone matrix is doped with 15% flaky graphene (thickness 2-5 nm); forming a three-dimensional heat conduction-energy dissipation network, which can reduce the 2000 Hz vibration acceleration by 18 dB and improve the heat dissipation efficiency by 30%.

[0071] In the embodiment of the present application, the corrugated buffer pad is arranged in a gradient pore configuration or in a honeycomb structure configuration.

[0072] In the embodiment of the present application, the viscoelastic damping layer includes a gradient-distributed carbon nanotube intermediate layer with a density of 5-15 mg / cm 3 The surface is equipped with a micro-nano pyramid array with a height of 50μm.

[0073] In an embodiment of the present application, a plurality of elastic clips are also provided at equal intervals on the inner wall of the shell, and the elastic clips are arranged in a cantilever beam structure, and a hemispherical protrusion is provided at the end of the elastic clip; wherein, the number of elastic clips is an integer multiple of the number of stator poles; preferably, there are 6 elastic clips (the number of stator poles is 6), and the diameter of the hemispherical protrusion at the end is 0.8 mm, so that when the stator assembly is assembled with the shell, the interference with the inner wall of the shell is 0.05 mm.

[0074] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention is disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technology of the present invention are all within the scope of the technical solution of the present invention without departing from the content of the technical solution of the present invention.

Claims

1. A method for assembling a micro motor, characterized in that: The following steps are involved: Step S1: Press the stator assembly into the housing at a preset phase angle so that the wedge-shaped protrusion and the annular groove generate axial force component locking; Step S2: Cool the bearing seat with liquid nitrogen and then press-fit the rotor shaft, and form an interference fit after returning to room temperature; Step S3: applying axial compression to the shape memory alloy ring when installing the end cover, and heating it until it triggers radial expansion; Step S4: Run the motor at the rated speed, and use centrifugal force to plastically deform the buffer pad at the bottom of the bearing seat so that it fits into the housing.

2. The micromotor assembly method according to claim 1, characterized in that: In step S2, the bearing seat is cooled to -196°C with liquid nitrogen, and the rotor shaft is press-fitted at a speed of 0.5 mm / s and a press-fitting pressure of 50 MPa. After returning to room temperature, an interference fit is formed between the bearing seat and the rotor shaft.

3. The micro motor assembly method according to claim 1, characterized in that: In step S2, the tapered bearing seat is completely immersed in liquid nitrogen, and the cooling rate is controlled according to a non-uniform gradient; the method for controlling the non-uniform gradient is: When cooling the conical surface area of the tapered bearing seat, the cooling rate is 50°C / min; When cooling the bottom area of the tapered bearing seat, the cooling rate is 30°C / min; The cooling time t is calculated based on the workpiece mass, formula: t = 0.05m 1.2 , where t is the cooling time and m is the workpiece mass.

4. The micromotor assembly method according to claim 1, characterized in that: In step S3, when installing the end cover, axial compression is applied to the shape memory alloy ring, and the ring is heated to 80-100° C. to trigger radial expansion.

5. The micro motor assembly method according to claim 1, characterized in that: In step S3, when the end cover is installed, axial compression is applied to the shape memory alloy ring. When the temperature is cooled to 20° C., the shape memory alloy ring contracts radially by 0.12%.

6. The micromotor assembly method according to claim 1, characterized in that: In step S2, the bearing seat is cooled by liquid nitrogen and then subjected to low-temperature tempering at 150° C. for 2 h.

7. The micro motor assembly method according to claim 1, characterized in that: In step S2, when the bearing seat is cooled by liquid nitrogen, the bearing seat is positioned on a turntable, and the turntable drives the bearing seat to rotate at a constant speed in the liquid nitrogen.

8. A micromotor structure formed according to the micromotor assembly method according to any one of claims 1 to 7, characterized in that: The invention comprises a shell, a stator assembly, a rotor shaft, a bearing seat and an end cover, wherein the inner wall of the shell is provided with an annular groove, the depth of the annular groove is gradually changed along the circumferential direction, the outer edge of the stator assembly is provided with a wedge-shaped protrusion which cooperates with the annular groove, the outer surface of the wedge-shaped protrusion is covered with a viscoelastic damping layer, the rotor shaft is pressed into the bearing seat, the bearing seat is conical, and the bottom of the bearing seat is provided with a corrugated buffer pad; the upper end of the shell is provided with an opening, the outer periphery of the lower end of the end cover is embedded with a shape memory alloy ring, the end cover is installed at the upper end of the shell and is used to close the opening, and when the end cover is installed at the upper end of the shell, the end cover is heated so that the shape memory alloy ring generates a radial pre-tightening force after the heat treatment and abuts and locks with the inner wall of the shell.

9. The micro motor structure according to claim 8, characterized in that: The viscoelastic damping layer is a silica gel-graphene composite material with a thickness of 0.1-0.3 mm and a loss factor of ≥0.

5.

10. The micro motor structure according to claim 8, characterized in that: The inner wall of the shell is also provided with a plurality of elastic buckles at equal intervals. The elastic buckles are arranged in a cantilever beam structure, and the ends of the elastic buckles are provided with hemispherical protrusions.

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