Keyless cooperation equipment dismounting and mounting method based on cooperation of cold contraction and heat expansion of liquid nitrogen

Abstract

The invention relates to the technical field of mechanical engineering, and discloses a keyless cooperation equipment disassembly and assembly method based on cooperation of cold contraction and heat expansion of liquid nitrogen, and the method comprises the steps of S1, early-stage general preparation, S2, specific disassembly, S3, specific assembly and S4, key quality control. Multi-point measurement is carried out on the outer diameter of the shaft and the inner hole of the mating part through a micrometer and a dial indicator tool (the measurement section of the outer diameter of the shaft is larger than or equal to 3, and the measurement mode of the inner hole is coaxial with the outer diameter of the shaft), the thermal expansion and cold shrinkage target size is calculated by combining the thermal expansion coefficient and the cold shrinkage coefficient of a part material, and it is ensured that the actual interference magnitude is stabilized within the design range of 0.08 mm-0. 1 mm; disassembly and assembly clamping stagnation or part damage caused by parameter deviation is effectively avoided, and the disassembly and assembly failure rate is reduced to the minimum.

Description

Technical Field

[0001] This invention relates to the field of mechanical engineering technology, specifically to a method for disassembling and assembling bondless fitting equipment based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion. Background Technology

[0002] Keyless fits, as a core fitting method in high-precision equipment, are widely used in various industrial transmission systems. Their interference fit typically needs to be controlled within 0.08mm-0.1mm (higher for large equipment) to ensure transmission stability and load-bearing capacity. However, existing disassembly and assembly processes for keyless fit equipment have many technical defects, making it difficult to meet the requirements for precise, safe, and efficient maintenance. Specific problems are as follows: The dimensional measurement and parameter calculation are crude: Current methods often employ single-point or simplified measurement before disassembly and assembly, failing to accurately measure the shaft's outer diameter and the gear / coupling's inner diameter at multiple points (e.g., ≥3 measurement sections for the shaft's outer diameter, each spaced 120° apart). This easily leads to misjudgments of the actual interference fit. Furthermore, the thermal expansion coefficient (11.5×10⁻⁻¹) of the component material (e.g., alloy steel, 45# steel) is not considered. 6 / ℃-13×10⁻ 6 The calculation of thermal expansion and contraction target dimensions using the coefficient of thermal expansion and contraction (°C) and the coefficient of thermal expansion and contraction often leads to assembly and disassembly jamming or component damage due to parameter deviations, resulting in a high failure rate.

[0003] Inadequate preparation and cleaning of tools and equipment: The existing process merely goes through the motions in inspecting key equipment such as multi-functional disassembly tools, heating equipment, and liquid nitrogen containers. The wear of the clamping surfaces of the disassembly fixtures, the temperature control system error of the heating equipment (often exceeding ±5℃), and the sealing of the liquid nitrogen container are not rigorously verified, which can easily lead to tool failure during disassembly and assembly. Furthermore, non-corrosive cleaning solvents are not used to thoroughly remove oil and rust from the surfaces of mating parts. Residual impurities can scratch the mating surfaces or affect the mating accuracy, requiring additional repair treatment afterward. Summary of the Invention

[0004] 1. Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method for disassembling and assembling keyless mating devices based on the synergistic effect of liquid nitrogen cooling and thermal expansion. This method has advantages such as improved accuracy in dimensional measurement and parameter calculation, and solves the problem of crude dimensional measurement and parameter calculation.

[0005] (II) Technical Solution To achieve the above-mentioned goal of improving the accuracy of dimensional measurement and parameter calculation, the present invention provides the following technical solution: a method for disassembling and assembling keyless mating equipment based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion, including S1 general preparation, S2 specific disassembly steps, S3 specific assembly steps and S4 key quality control points. The S1 general preparation includes S101 accurate dimensional measurement and parameter calculation, S102 tool and equipment inspection and debugging and S103 safety protection and environmental control. The specific steps of disassembly in S2 include S201 thermal expansion pretreatment of mating parts, S202 precise disassembly execution, and S203 post-disassembly component inspection and recording. The specific assembly steps of S3 include liquid nitrogen cooling and shrinkage treatment of the S301 shaft, synchronous thermal expansion treatment of mating parts of S302, rapid and precise assembly operation of S303, and post-assembly curing and testing verification of S304. Among them, the key quality control points of S4 include S401 avoiding excessive temperature difference and S402 test verification support.

[0006] Preferably, S101 involves precise dimensional measurement and parameter calculation; Use a micrometer, dial indicator, or inside dial indicator to measure the key dimensions of keyless mating parts at multiple points, including the outer diameter of the shaft and the inner diameter of the gear / coupling. Record the actual interference fit (which must be within the design range of 0.08mm-0.1mm). Based on the measurement data, combined with the coefficient of thermal expansion and coefficient of thermal contraction of the component material, calculate the target size that the inner hole needs to expand when thermally expanding and the target size that the shaft needs to shrink when coldly contracting, to avoid disassembly and assembly failure due to parameter deviations.

[0007] Preferably, the tools and equipment in step S102 are inspected and debugged; Prepare a multi-functional disassembly tool, industrial-grade liquid nitrogen, electromagnetic induction heating equipment, a contact thermometer (measuring range -200℃-300℃), a surface roughness tester, and a non-corrosive cleaning solvent. Check the tools for integrity: the clamping surfaces of the disassembly fixture should be free of wear, the liquid nitrogen container should be leak-free, and the temperature control system error of the heating equipment should be ≤±2℃. Wipe the surfaces of mating parts with a cleaning solvent to remove oil, rust, and other impurities to prevent impurities from affecting the mating accuracy or scratching the surface of the parts.

[0008] Preferably, S103 includes safety protection and environmental control; Operators should wear low-temperature protective gloves (resistant to -196℃), heat-resistant gloves, goggles, and anti-static work clothes; set up warning signs in the operating area and remove irrelevant debris; control the ambient temperature to 15℃-25℃ and humidity to ≤60% to prevent moisture in the air from condensing on the surface of the components in a low-temperature environment.

[0009] Preferably, the S201 mating part undergoes thermal expansion pretreatment; Fix the gear or coupling to be disassembled onto the heating fixture, ensuring that the coaxiality deviation of the parts is ≤0.03mm. Start the electromagnetic induction heating equipment and adopt the "step heating" method: initially, heat to 100℃-120℃ at a rate of 5℃ / min and hold for 5 minutes; then heat to the target temperature at a rate of 3℃ / min. Monitor the surface temperature of the parts with a contact thermometer throughout the process and record the data every 2 minutes to avoid local overheating that may cause changes in the metallographic structure of the material. If the temperature exceeds the target value ±5℃, immediately stop heating and allow it to cool naturally to a reasonable range.

[0010] Preferably, S202 is performed with precise disassembly; After the component has expanded to the target size and been kept warm for 2 minutes, align the clamping assembly of the multi-functional disassembly tool with the end face of the gear / coupling, ensuring that the tool and the component are coaxial. Activate the hydraulic jacking assembly and slowly apply axial thrust at a pressure rate of 0.5 MPa / min. The thrust magnitude is calculated based on the weight of the component. During the disassembly process, use a dial indicator to monitor the radial runout of the shaft in real time. If the runout exceeds 0.02 mm, immediately adjust the tool clamping position to ensure a smooth disassembly process. When the separation distance between the mating part and the shaft reaches 5 mm-10 mm, reduce the thrust rate to 0.2 MPa / min until complete separation.

[0011] Preferably, the components are inspected and recorded after disassembly in step S203; Place the disassembled shaft and gear / coupling on dry wooden blocks and allow them to cool naturally to room temperature. Use a surface roughness tester to check the roughness of the mating surfaces and inspect for scratches, dents, cracks, or other defects. Measure the outer diameter of the shaft and the inner diameter of the mating parts again, record the dimensional changes, and create a disassembly file to provide a reference for subsequent assembly.

[0012] Preferably, the S301 shaft undergoes liquid nitrogen cooling shrinkage treatment; Place the shaft vertically into the liquid nitrogen container, ensuring the mating section is completely submerged. Adjust the cooling and shrinkage time according to the shaft diameter: 15-20 minutes for a diameter of 50mm-80mm; 20-25 minutes for a diameter of 80mm-120mm. Every 5 minutes, use a long-handled caliper to measure the outer diameter of the mating section until the size is reduced to "0.06mm-0.09mm smaller than the original diameter of the inner hole of the mating part". After cooling and shrinkage is complete, quickly remove the shaft from the liquid nitrogen and wipe the frost layer that has condensed on the surface with a dry cotton cloth to prevent moisture residue from remaining after the frost melts and causes corrosion. S302 mating parts undergo synchronous thermal expansion treatment; While the shaft is being cooled and shrunk, the gears or couplings are being thermally expanded, but the target temperature needs to be slightly lower to ensure that the diameter of the inner hole after thermal expansion is 0.03mm-0.06mm larger than the outer diameter of the shaft after cooling and shrinking. This ensures that the shaft can fit together smoothly during assembly and avoids excessive gaps that could affect subsequent use. During the thermal expansion process, the temperature also needs to be monitored in real time, with data recorded every minute to ensure temperature stability.

[0013] Preferably, the S303 is a rapid and precise assembly operation; After the shaft is removed from the liquid nitrogen after cooling and shrinking, it needs to be assembled within 3-5 minutes. Align the mating section of the shaft with the inner hole of the thermally expanded gear / coupling. Guide the axial movement of the shaft with a positioning fixture. The coaxiality error of the positioning fixture must be ≤0.02mm. Use a "slow push-in" method during assembly. Gently tap the end face of the shaft with a rubber hammer until the stepped surface of the shaft fits against the end face of the mating part. After assembly, use a dial indicator to measure the radial runout at both ends of the shaft to ensure that the runout is ≤0.02mm. If the runout exceeds the standard, the position of the mating part needs to be finely adjusted until it meets the requirements. S304 post-assembly curing and testing verification; After assembly, allow the components to naturally return to room temperature. During this period, do not touch or move the components to avoid displacement of the mating surfaces. After the temperature has fully recovered, measure the radial runout and end face runout of the mating parts again to confirm that they meet the technical requirements. Then, conduct a "no-load test run": connect the assembled equipment to the drive unit and run it without load for 1 hour, monitoring the vibration value of the shaft and the bearing temperature. Then, load it to 80% of the rated load and run it for 2 hours, continuously tracking the vibration, temperature, and noise indicators. If all parameters are stable, the assembly is considered qualified. Finally, organize all the data from the assembly process to form an assembly file, providing experience reference for the maintenance of similar equipment.

[0014] Preferably, S401 avoids excessive temperature difference: the difference between the highest temperature during thermal expansion and the lowest temperature during thermal contraction should be controlled within 300°C to prevent the component from cracking due to excessive thermal stress. S402 test verification support: When applied to a new type of keyless mating equipment for the first time, at least three disassembly and assembly tests should be conducted on the same specification of the off-line parts to track the dimensional stability and mechanical properties of the parts after the tests. After confirming the feasibility of the method, it can be applied to actual maintenance.

[0015] (III) Beneficial Effects Compared with the prior art, the present invention provides a method for disassembling and assembling bondless devices based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion, which has the following beneficial effects: 1. This method for disassembling and assembling keyless mating equipment based on the synergistic effect of liquid nitrogen thermal expansion and contraction improves the accuracy of dimensional measurement and parameter calculation, avoiding disassembly and assembly failures: Multiple measurements are performed on the shaft's outer diameter and the mating parts' inner hole using micrometers and dial indicators (≥3 measurement sections for the shaft's outer diameter, and the inner hole measurement method is the same as for the shaft's outer diameter). The target dimensions for thermal expansion and contraction are calculated by combining the thermal expansion coefficient and cold contraction coefficient of the component materials, ensuring that the actual interference fit remains stable within the design range of 0.08mm-0.1mm. This effectively avoids disassembly and assembly jamming or component damage caused by parameter deviations, minimizing the disassembly and assembly failure rate.

[0016] 2. This method for disassembling and assembling keyless mating equipment based on the synergistic effect of liquid nitrogen's thermal expansion and contraction ensures the reliability of tools and equipment and eliminates interference from impurities: by strictly inspecting the clamping surface of the multi-functional disassembly tool (no wear), the temperature control system of the heating equipment (error ≤ ±2℃), and the liquid nitrogen container (no leakage), the stable operation of the equipment is ensured; at the same time, non-corrosive cleaning solvents are used to thoroughly remove oil and rust from the surface of mating parts, avoiding impurities from scratching the mating surface or affecting the mating accuracy, reducing subsequent repair procedures, and lowering maintenance costs.

[0017] 3. This method for disassembling and assembling keyless mating equipment based on the synergistic effect of liquid nitrogen's thermal expansion and contraction enhances safety protection and environmental stability, and avoids operational risks: it requires operators to wear protective gloves resistant to -196℃, heat-resistant gloves, and goggles to prevent frostbite and burns; it controls the operating environment at 15℃-25℃ and humidity ≤60% to prevent moisture from condensing on the surface of components at low temperatures, thus preventing corrosion of mating surfaces or dimensional deviations due to thermal contraction, and ensuring environmental stability and personnel safety during the disassembly and assembly process.

[0018] 4. This method for disassembling and assembling keyless mating equipment based on the synergistic effect of liquid nitrogen cooling and thermal expansion optimizes the thermal expansion and contraction process to prevent component damage: During the thermal expansion stage, a "step-wise heating" method is adopted (heating at 5℃ / min to 100℃-120℃ and holding for 5 minutes, then increasing to the target temperature at 3℃ / min), with the temperature recorded every 2 minutes. If the temperature exceeds the target value by ±5℃, the process is immediately paused to effectively prevent changes in the metallographic structure of the material caused by local overheating; During the cooling and contraction stage, the time is precisely adjusted according to the shaft diameter (15-20 minutes for 50mm-80mm, 20-25 minutes for 80mm-120mm), and the dimensions are measured every 5 minutes to ensure accurate shaft shrinkage; At the same time, the difference between the highest thermal expansion temperature and the lowest cooling and contraction temperature is controlled to be ≤300℃ to avoid thermal stress cracks in the components and protect the mechanical properties of the components. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] This solution provides a technical solution, specifically, a method for disassembling and assembling bondless mating equipment based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion, including the following method: S1 General preparation in the early stage; Before carrying out disassembly or assembly operations, basic preparatory work must be completed to lay the foundation for subsequent precise operations: S101 precise dimensional measurement and parameter calculation; Use a micrometer, dial indicator, or inside dial indicator to measure the key dimensions of keyless mating parts at multiple points, including the outer diameter of the shaft and the inner diameter of the gear / coupling. Record the actual interference fit (which must be within the design range of 0.08mm-0.1mm). Based on the measurement data, combined with the coefficient of thermal expansion and coefficient of thermal contraction of the component material, calculate the target size that the inner hole needs to expand when thermally expanding and the target size that the shaft needs to shrink when coldly contracting, to avoid disassembly and assembly failure due to parameter deviations. S102 Tool and equipment inspection and debugging; Prepare a multi-functional disassembly tool, industrial-grade liquid nitrogen, electromagnetic induction heating equipment, a contact thermometer (measuring range -200℃-300℃), a surface roughness tester, and a non-corrosive cleaning solvent. Check the tools for integrity: the clamping surfaces of the disassembly fixture should be free of wear, the liquid nitrogen container should be leak-free, and the temperature control system error of the heating equipment should be ≤±2℃. Wipe the surfaces of mating parts with a cleaning solvent to remove oil, rust, and other impurities to prevent impurities from affecting the mating accuracy or scratching the surface of the parts. S103 Safety Protection and Environmental Control; Operators should wear low-temperature protective gloves (resistant to -196℃), heat-resistant gloves, goggles, and anti-static work clothes; set up warning signs in the operating area and remove irrelevant debris; control the ambient temperature to 15℃-25℃ and humidity to ≤60% to prevent moisture in the air from condensing on the surface of the components in a low-temperature environment; S2 disassembly specific steps; S201 mating parts thermal expansion pretreatment; Fix the gear or coupling to be disassembled onto the heating fixture, ensuring that the coaxiality deviation of the parts is ≤0.03mm. Start the electromagnetic induction heating equipment and adopt the "step heating" method: initially, heat up to 100℃-120℃ at a rate of 5℃ / min and hold for 5 minutes; then heat up to the target temperature at a rate of 3℃ / min. Monitor the surface temperature of the parts with a contact thermometer throughout the process and record the data every 2 minutes to avoid local overheating that may cause changes in the metallographic structure of the material. If the temperature exceeds the target value ±5℃, immediately stop heating and allow it to cool naturally to a reasonable range. S202 Precision disassembly execution; After the component has expanded to the target size and been kept warm for 2 minutes, align the clamping assembly of the multi-functional disassembly tool with the end face of the gear / coupling, ensuring that the tool and the component are coaxial. Activate the hydraulic jacking assembly and slowly apply axial thrust at a pressure rate of 0.5 MPa / min. The thrust magnitude is calculated based on the weight of the component. During the disassembly process, use a dial indicator to monitor the radial runout of the shaft in real time. If the runout exceeds 0.02 mm, immediately adjust the tool clamping position to ensure a smooth disassembly process. When the separation distance between the mating part and the shaft reaches 5 mm-10 mm, reduce the thrust rate to 0.2 MPa / min until complete separation. S203 Component inspection and recording after disassembly; Place the disassembled shaft and gear / coupling on dry wooden blocks and allow them to cool naturally to room temperature. Use a surface roughness tester to check the roughness of the mating surfaces and inspect for scratches, dents, cracks, or other defects. Measure the outer diameter of the shaft and the inner diameter of the mating parts again, record the dimensional changes, and create a disassembly file to provide a reference for subsequent assembly. S3 assembly specific steps; Liquid nitrogen cooling and shrinkage treatment of S301 shaft; Place the shaft vertically into the liquid nitrogen container, ensuring the mating section is completely submerged. Adjust the cooling and shrinkage time according to the shaft diameter: 15-20 minutes for a diameter of 50mm-80mm; 20-25 minutes for a diameter of 80mm-120mm. Every 5 minutes, use a long-handled caliper to measure the outer diameter of the mating section until the size is reduced to "0.06mm-0.09mm smaller than the original diameter of the inner hole of the mating part". After cooling and shrinkage is complete, quickly remove the shaft from the liquid nitrogen and wipe the frost layer that has condensed on the surface with a dry cotton cloth to prevent moisture residue from remaining after the frost melts and causes corrosion. S302 mating parts undergo synchronous thermal expansion treatment; While the shaft is being cooled and shrunk, the gear or coupling is being thermally expanded, but the target temperature needs to be slightly lower to ensure that the diameter of the inner hole after thermal expansion is 0.03mm-0.06mm larger than the outer diameter of the shaft after cooling and shrinkage. This ensures that the shaft can fit together smoothly during assembly and avoids excessive clearance that could affect subsequent use. During the thermal expansion process, the temperature also needs to be monitored in real time, and data should be recorded every minute to ensure temperature stability. S303 rapid and precise assembly operation; After the shaft is removed from the liquid nitrogen after cooling and shrinking, it needs to be assembled within 3-5 minutes. Align the mating section of the shaft with the inner hole of the thermally expanded gear / coupling. Guide the axial movement of the shaft with a positioning fixture. The coaxiality error of the positioning fixture must be ≤0.02mm. Use a "slow push-in" method during assembly. Gently tap the end face of the shaft with a rubber hammer until the stepped surface of the shaft fits against the end face of the mating part. After assembly, use a dial indicator to measure the radial runout at both ends of the shaft to ensure that the runout is ≤0.02mm. If the runout exceeds the standard, the position of the mating part needs to be finely adjusted until it meets the requirements. S304 post-assembly curing and testing verification; After assembly, allow the components to naturally return to room temperature. During this period, do not touch or move the components to avoid displacement of the mating surfaces. After the temperature has fully recovered, measure the radial runout and end face runout of the mating parts again to confirm that they meet the technical requirements. Then, conduct a "no-load test run": connect the assembled equipment to the drive unit and run it without load for 1 hour, monitoring the vibration value of the shaft and the bearing temperature. Then, load it to 80% of the rated load and run it for 2 hours, continuously tracking the vibration, temperature, and noise indicators. If all parameters are stable, the assembly is considered qualified. Finally, organize all the data from the assembly process to form an assembly file, providing experience reference for the maintenance of similar equipment. S4 Key Quality Control Points; The temperature and time for thermal expansion and contraction must be strictly matched with the interference fit: when the interference fit is 0.08mm, the target temperature for thermal expansion can be appropriately reduced, and the contraction time can be shortened by 2-3 minutes; when the interference fit is 0.1mm, the thermal expansion temperature needs to be appropriately increased and the contraction time extended to ensure that the dimensional change meets the disassembly and assembly requirements. S401 Avoid excessive temperature difference: The difference between the highest temperature during thermal expansion and the lowest temperature during thermal contraction must be controlled within 300℃ to prevent cracks in the components due to excessive thermal stress. S402 test demonstration support: When applied to a new type of keyless mating equipment for the first time, at least three disassembly and assembly tests should be conducted on the same specification of the off-line parts to track the dimensional stability and mechanical properties of the parts after the tests. After confirming the feasibility of the method, it can be applied to actual maintenance. Furthermore, this method improves the accuracy of dimensional measurement and parameter calculation, avoiding disassembly and assembly failures: by using micrometers and dial indicators to measure the outer diameter of the shaft and the inner hole of the mating parts at multiple points (≥3 measurement sections for the outer diameter of the shaft, and the same measurement method for the inner hole as for the outer diameter of the shaft), and by combining the thermal expansion coefficient and cold contraction coefficient of the component material, the target dimensions for thermal expansion and contraction are calculated to ensure that the actual interference fit is stable within the design range of 0.08mm-0.1mm, effectively avoiding disassembly and assembly jamming or component damage caused by parameter deviations, and minimizing the disassembly and assembly failure rate; Furthermore, this method ensures the reliability of tools and equipment and eliminates interference from impurities: by strictly inspecting the clamping surface of the multi-functional disassembly tool (no wear), the temperature control system of the heating equipment (error ≤ ±2℃), and the liquid nitrogen container (no leakage), the stable operation of the equipment is ensured; at the same time, non-corrosive cleaning solvents are used to thoroughly remove oil and rust from the surface of mating parts, avoiding impurities from scratching the mating surfaces or affecting the mating accuracy, reducing subsequent repair procedures, and lowering maintenance costs; Furthermore, this method enhances safety protection and environmental stability, and avoids operational risks: it requires operators to wear protective gloves that can withstand temperatures as low as -196℃, heat-resistant gloves, and goggles to prevent frostbite and burns; it controls the operating environment at 15℃-25℃ and humidity ≤60% to prevent moisture from condensing on the surface of parts at low temperatures, prevent corrosion of mating surfaces or dimensional deviations due to cold shrinkage, and ensure environmental stability and personnel safety during the disassembly and assembly process. Furthermore, this method optimizes the thermal expansion and contraction process to prevent component damage: during the thermal expansion stage, a "step-wise heating" method is adopted (heating at 5℃ / min to 100℃-120℃ and holding for 5 minutes, then increasing to the target temperature at 3℃ / min), with the temperature recorded every 2 minutes. If the temperature exceeds the target value by ±5℃, the process is immediately paused to effectively prevent changes in the metallographic structure of the material caused by local overheating; during the cooling and contraction stage, the time is precisely adjusted according to the shaft diameter (15-20 minutes for 50mm-80mm, 20-25 minutes for 80mm-120mm), and the dimensions are measured every 5 minutes to ensure accurate shaft shrinkage; at the same time, the difference between the highest thermal expansion temperature and the lowest cooling and contraction temperature is controlled to be ≤300℃ to avoid thermal stress cracks in the component and protect the mechanical properties of the component; Furthermore, this method standardizes post-disassembly inspection and application to new equipment, ensuring assembly quality: after disassembly, the components are placed on dry wooden blocks to cool naturally, and the Ra value of the mating surfaces is measured using a surface roughness meter (ensuring ≤1.6μm). Dimensional change data is recorded to form a disassembly file, providing accurate reference for subsequent assembly. When first applied to new equipment, at least three disassembly and assembly tests are conducted using components of the same specification to verify dimensional stability and mechanical properties before actual maintenance, avoiding risks associated with new equipment application and improving process adaptability. Furthermore, this method shortens the assembly cycle and ensures long-term stable operation: the cold-shrink shaft is assembled within 3-5 minutes, guided axial movement by positioning fixtures (coaxiality error ≤0.02mm), and "slow push-in" combined with gentle tapping with a rubber hammer to ensure precise fit between the shaft and mating parts; after assembly, it is cured at room temperature, tested under no-load (1 hour, monitoring vibration value and bearing temperature), and operated at 80% rated load (2 hours), and all process data is recorded to form an assembly archive. This not only ensures the assembly qualification rate (radial runout ≤0.02mm), but also provides reusable experience for the maintenance of similar equipment, while shortening production line downtime and improving equipment operation and maintenance efficiency.

[0021] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for disassembling and assembling bondless fitting equipment based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion, comprising S1 general preparation, S2 specific disassembly steps, S3 specific assembly steps, and S4 key quality control points, characterized in that: The general preparations in the early stage of S1 include S101 precise measurement of dimensions and parameter calculation, S102 tool and equipment inspection and debugging, and S103 safety protection and environmental control. The specific steps of disassembly in S2 include S201 thermal expansion pretreatment of mating parts, S202 precise disassembly execution, and S203 post-disassembly component inspection and recording. The specific steps of S3 assembly include S301 liquid nitrogen cooling and shrinkage treatment of the shaft, S302 synchronous thermal expansion treatment of mating parts, S303 rapid and precise assembly operation, and S304 post-assembly curing and testing verification. Among them, the key quality control points of S4 include S401 avoiding excessive temperature difference and S402 test verification support.

2. The method for disassembling and assembling a bondless device based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion, as described in claim 1, is characterized in that: The precise measurement and parameter calculation of S101 dimensions; Use a micrometer, dial indicator, or inside dial indicator to measure the key dimensions of keyless mating parts at multiple points, including the outer diameter of the shaft and the inner diameter of the gear / coupling. Record the actual interference fit (which must be within the design range of 0.08mm-0.1mm). Based on the measurement data, combined with the coefficient of thermal expansion and coefficient of thermal contraction of the component material, calculate the target size that the inner hole needs to expand when thermally expanding and the target size that the shaft needs to shrink when coldly contracting, to avoid disassembly and assembly failure due to parameter deviations.

3. The method for disassembling and assembling a bondless device based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion, as described in claim 1, is characterized in that: The S102 tool and equipment are inspected and debugged; Prepare a multi-functional disassembly tool, industrial-grade liquid nitrogen, electromagnetic induction heating equipment, a contact thermometer (measuring range -200℃-300℃), a surface roughness tester, and a non-corrosive cleaning solvent. Check the tools for integrity: the clamping surfaces of the disassembly fixtures should be free of wear, the liquid nitrogen container should be leak-free, and the temperature control system error of the heating equipment should be ≤±2℃. Wipe the surfaces of mating parts with a cleaning solvent to remove oil, rust, and other impurities to prevent impurities from affecting the mating accuracy or scratching the surface of the parts.

4. The method for disassembling and assembling a bondless device based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion, as described in claim 1, is characterized in that: S103 Safety Protection and Environmental Control; Operators should wear low-temperature protective gloves (resistant to -196℃), heat-resistant gloves, goggles, and anti-static work clothes; set up warning signs in the operating area and remove irrelevant debris; control the ambient temperature to 15℃-25℃ and humidity to ≤60% to prevent moisture in the air from condensing on the surface of the components in a low-temperature environment.

5. The method for disassembling and assembling a bondless device based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion, as described in claim 1, is characterized in that: The S201 mating part undergoes thermal expansion pretreatment; Fix the gear or coupling to be disassembled onto the heating fixture, ensuring that the coaxiality deviation of the parts is ≤0.03mm. Start the electromagnetic induction heating equipment and adopt the "step heating" method: initially, heat to 100℃-120℃ at a rate of 5℃ / min and hold for 5 minutes; then heat to the target temperature at a rate of 3℃ / min. Monitor the surface temperature of the parts with a contact thermometer throughout the process and record the data every 2 minutes to avoid local overheating that may cause changes in the metallographic structure of the material. If the temperature exceeds the target value ±5℃, immediately stop heating and allow it to cool naturally to a reasonable range.

6. The method for disassembling and assembling a bondless device based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion according to claim 1, characterized in that: The precise disassembly of S202 is performed; After the component has expanded to the target size and been kept warm for 2 minutes, align the clamping assembly of the multi-functional disassembly tool with the end face of the gear / coupling, ensuring that the tool and the component are coaxial. Activate the hydraulic jacking assembly and slowly apply axial thrust at a pressure rate of 0.5 MPa / min. The thrust magnitude is calculated based on the weight of the component. During the disassembly process, use a dial indicator to monitor the radial runout of the shaft in real time. If the runout exceeds 0.02 mm, immediately adjust the tool clamping position to ensure a smooth disassembly process. When the separation distance between the mating part and the shaft reaches 5 mm-10 mm, reduce the thrust rate to 0.2 MPa / min until complete separation.

7. The method for disassembling and assembling a bondless device based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion, as described in claim 1, is characterized in that: S203 Inspection and recording of components after disassembly; Place the disassembled shaft and gear / coupling on dry wooden blocks and allow them to cool naturally to room temperature. Use a surface roughness tester to check the roughness of the mating surfaces and inspect for scratches, dents, cracks, or other defects. Measure the outer diameter of the shaft and the inner diameter of the mating parts again, record the dimensional changes, and create a disassembly file to provide a reference for subsequent assembly.

8. The method for disassembling and assembling a bondless device based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion according to claim 1, characterized in that: The S301 shaft undergoes liquid nitrogen cooling and shrinkage treatment; Place the shaft vertically into the liquid nitrogen container, ensuring the mating section is completely submerged. Adjust the cooling time according to the shaft diameter: 15-20 minutes for a diameter of 50mm-80mm; 20-25 minutes for a diameter of 80mm-120mm. Every 5 minutes, use a long-handled caliper to measure the outer diameter of the mating section until the size is reduced to "0.06mm-0.09mm smaller than the original diameter of the inner hole of the mating part". After cooling is complete, quickly remove the shaft from the liquid nitrogen and wipe the frost layer on the surface with a dry cotton cloth to prevent moisture residue from remaining after the frost melts and causes corrosion. S302 mating parts undergo synchronous thermal expansion treatment; While the shaft is being cooled and shrunk, the gears or couplings are being thermally expanded, but the target temperature needs to be slightly lower to ensure that the diameter of the inner hole after thermal expansion is 0.03mm-0.06mm larger than the outer diameter of the shaft after cooling and shrinking. This ensures that the shaft can fit together smoothly during assembly and avoids excessive gaps that could affect subsequent use. During the thermal expansion process, the temperature also needs to be monitored in real time, with data recorded every minute to ensure temperature stability.

9. The method for disassembling and assembling a bondless device based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion, as described in claim 1, is characterized in that: The S303 rapid and precise assembly operation; After the shaft is removed from the liquid nitrogen after cooling and shrinking, it needs to be assembled within 3-5 minutes. Align the mating section of the shaft with the inner hole of the thermally expanded gear / coupling. Guide the axial movement of the shaft with a positioning fixture. The coaxiality error of the positioning fixture must be ≤0.02mm. Use the "slow push-in" method during assembly. Gently tap the end face of the shaft with a rubber hammer until the stepped surface of the shaft fits against the end face of the mating part. After assembly, use a dial indicator to measure the radial runout at both ends of the shaft to ensure that the runout is ≤0.02mm. If the runout exceeds the standard, the position of the mating part needs to be finely adjusted until it meets the requirements. S304 post-assembly curing and testing verification; After assembly, allow the components to naturally return to room temperature. During this period, do not touch or move the components to avoid displacement of the mating surfaces. After the temperature has fully recovered, measure the radial runout and end face runout of the mating parts again to confirm that they meet the technical requirements. Then, conduct a "no-load test run": connect the assembled equipment to the drive unit and run it without load for 1 hour, monitoring the vibration value of the shaft and the bearing temperature. Then, load it to 80% of the rated load and run it for 2 hours, continuously tracking the vibration, temperature, and noise indicators. If all parameters are stable, the assembly is considered qualified. Finally, organize all the data from the assembly process to form an assembly file, providing experience reference for the maintenance of similar equipment.

10. The method for disassembling and assembling a bondless device based on the synergistic effect of liquid nitrogen cooling contraction and thermal expansion according to claim 1, characterized in that: S401 avoids excessive temperature difference: the difference between the highest temperature during thermal expansion and the lowest temperature during thermal contraction must be controlled within 300℃ to prevent the component from cracking due to excessive thermal stress. S402 test verification support: When applied to a new type of keyless mating equipment for the first time, at least three disassembly and assembly tests should be conducted on the same specification of the off-line parts to track the dimensional stability and mechanical properties of the parts after the tests. After confirming the feasibility of the method, it can be applied to actual maintenance.