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In this study, a three-dimensional model of the planetary gear train with straight cylindrical gears is established, and a virtual prototype model is constructed by using dynamics simulation software. Through the dynamics analysis, the accuracy and feasibility of the virtual prototype simulation model are verified. The study shows that the supporting stiffness of each component in the transmission system has a significant effect on the uniform load characteristics, and the change of the supporting stiffness of the planetary gear has the most sensitive effect on the uniform load characteristics. The uniform load characteristics of the transmission system is not sensitive to the change of the flexible supporting stiffness of the sun gear, but it is more sensitive to the change of the flexible supporting stiffness of the planetary gear, and the uniform load coefficient has obvious changes. The effect of gear tooth meshing stiffness changes on the uniform load characteristics of the transmission system is independent, simultaneously reducing the internal and external meshing stiffness has a more obvious uniform load effect than reducing the meshing stiffness alone.

The distribution of the load on the tooth surface greatly affects the performance of the power split of the planetary transmission system. This study mainly studies the load sharing characteristics of the planetary gear transmission system and summarizes the current research status of this problem. The basic problems related to load sharing are expounded. Then, the analysis methods and calculation models of load sharing characteristics in planetary transmission are compared and analyzed. The methods and mechanisms of load-sharing which are commonly used at present are reviewed. It can be found that error is the root cause of uneven load distribution, and the most effective way to improve the uniform load is to reduce the sensitivity of the system to error. At present, dynamic analysis and the influence of nonlinear factors are the focus of research on uniform load problems. Floating parts and flexible parts are still commonly used uniform load methods.

In order to analyze the lubrication characteristics of the planetary gear transmission of shield main drive reducers, a simulation model of splash lubrication of the single-stage planetary gear train is established using the moving particle semi-implicit (MPS) method. By comparing the distribution of lubricating oil particles, velocity field, pressure field, the number of lubricating oil particles in the meshing area of gear teeth and the churning resistance moment produced by each rotating part during the planetary gear train movement under different working conditions, the influence of input speed, initial oil level height and oil temperature on the system lubrication effect and churning loss power are studied. The results show that the oil particle velocity and pressure increase with the increase of the input speed and oil level, and the low speed and oil level height will lead to the uneven distribution of oil particles in the reducer. The number of particles in the meshing zone between planetary gears, sun gears and inner gear rings decreases with the increase of input speed and oil temperature, and decreases with the decrease of oil level height. The meshing area of sun gears is the risk area of poor lubrication. The power loss of the system is most significantly affected by the input speed, and increases exponentially with the increase of the speed, while the influence of oil level height and oil temperature is relatively small. In each working condition, the churning loss power generated by the three planetary gears takes the largest proportion in the total churning loss power.

The tooth surface friction has an important impact on the tooth surface contact stress and the tooth surface contact fatigue life. In the estimation of the contact fatigue life of the tooth surface, the influence of the friction force of the tooth surface is often ignored, which is not conducive to the accurate prediction of the contact fatigue life of the tooth surface. In order to accurately predict the contact fatigue life of the tooth surface, the R-S-N curves are fitted based on the three-parameter Weibull distribution and the nominal stress method according to the tooth surface contact fatigue test data of 18CrNiMo7-6 gear material. By calculating the contact stress on the tooth surface, the time-varying friction factor is introduced, and the influence of the time-varying friction factor on the contact fatigue life of the tooth surface is analyzed. Finally, the tooth surface contact fatigue test is used to verify the validity. The results show that the contact fatigue limit of tooth surface estimated by the traditional nominal stress method is large due to the influence of the time-varying friction factor, and the influence of the friction factor on contact fatigue life of tooth surfaces decreases with the increase of stress.

Aiming at the problem that the rack and pinion for the Three Gorges ship lift may face fatigue failure during its whole life cycle, the load spectrum including the stressed tooth surface and the number of load cycles is constructed in this study based on the rack and pinion load calculated by the torques of the driving motors and the synchronous shafts. Combined with the S-N curve of racks and Miner's linear cumulative damage criterion, the damage degree and residual fatigue life of racks within 35 years of design life are calculated. In addition, the cumulative iteration method is used to calculate the contact and bending safety factors of the rack, which realizes the comparison between the actual load and the design load of the rack and the operation safety performance verification. The results show that, the upper tooth surface of the rack has more meshing times, and its probability is 73.03%. During the design life, the total contact fatigue damage degree of the upper tooth surface of the rack is 1.65×10-12, and the total number of cycles according to the load spectrum is 1.87×1017. The total damage degree of the bending fatigue of the upper tooth surface of the rack is 8.15×10-14; the total number of cycles according to the load spectrum is 3.78×1018; the rack has a long residual fatigue life after 35 years of design life. The contact safety factor of the racks SH=2.958, bending safety factor SF=8.106, are both greater than the selected minimum safety factor under high reliability and the calculated safety factor under design load, and the safety margin of ship lift racks is sufficient. The research content of this study has enriched the relevant research in the field of fatigue life of super-large modulus racks and pinions, and provides theoretical basis and data support for the operation and maintenance of the Three Gorges ship lift.

The rack and pinion of the three gorges ship lift is a low speed and heavy load open gear transmission with hard tooth surface. Once the lubrication is poor, it is easy to cause damage such as tooth surface scuffing, which will affect the operation safety and reliability of the ship lift. This study is based on the actual operation data of the three gorges ship lift, and the lubrication of racks and pinions under various typical service conditions is systematically analyzed using the oil film thickness criterion. The relationship between the false water depth and the film thickness ratio in the ship compartment is deduced and the film thickness ratio of the lubrication state of the most dangerous meshing point under typical false water depth is calculated when the ship compartment is under constant speed. The worst lubrication condition of the rack and pinion is determined when the ship compartment is ascending and descending with variable speeds, and the relationship between the water depth in the ship compartment and the lubrication condition under variable speed typical operating conditions is analyzed. The position where the scuffing damage is more likely to occur is further determined. The results show that, when the ship lift is running at a constant speed, the lubrication state of the rack and pinion is the best under the optimum water depth in the ship compartment, and the film thickness ratio of the deviation from the optimal water level decreases with the power function λ∝±Δh-0.13 of the false water depth. When the rack and pinion is at the most dangerous meshing point, the root of the pinion and the top of the rack are in contact, and the lubrication condition between tooth surfaces is worse under large false water depth. When the ship lift moves at variable speeds, the working condition with poor lubrication condition is the upward acceleration and downward deceleration when the water depth of the ship chamber is 3.6 m. Due to the high contact frequency of the upper tooth surface on the rack and poor lubrication state, the risk of scuffing damage is higher.

Compared with ISO 6336:1996 edition，there are great changes in the latest edition of ISO/FDIS 6336-1 to 3：2019, in particular, the calculation of the helix angle factor for helical gear has a subversive change. In order to facilitate the reader to understand the changes of the new ISO 6336, the main changes in the content of different editions of ISO 6336 are introduced, the influences of the helix angle factors and single pair tooth contact factor on safety factor before and after modification are analyzed, and the influence of helix angle on the calculation results of contact strength and bending strength are discussed here with examples.

The rack test device for the Three Gorges ship lift is mainly composed of four parts: driving gearbox,driving gear-rack,loading gear-rack and loading gearbox. In order to better calculate and analyze the transmission efficiency of the rack test device,through the establishing gearbox transmission efficiency calculation model,transmission efficiencies of the four parts and the transmission efficiency and the power consumption of the total whole unit are calculated respectively,the calculation results are contrastive analyzed by the input speed and torque,output speed and torque of the test data,the accuracy of calculation model and test data is verified,the research basis of transmission efficiency of gearbox and gear rack for low speed and load duty is established.

The calculation method of equivalent load for crane reducer under variable load condition is analyzed. Application factor formulas for the calculation of gear fatigue strength and bearing fatigue life are deduced,and the index value of the fatigue strength calculation of gear is recalculated based on the life coefficient. In addition,the differences of load spectral coefficients in gear and bearing fatigue calculations are pointed out. The calculation method has a guiding significance for the design and calculation of crane reducer.

According to the forming process principle,the influence of the tooth profile modification,helix modification and tooth profile deviation,helix deviation and eccentricity tolerance of radial run-out of the involute helical gear on tooth profile shape is analyzed. The curve equations of the involute transverse tooth profile are derived step by step. By using the software,the curve equation of deviation is fitted,and the theoretical curve is replaced by the deviation curve. Then,the actual tooth profile model and solid model including modification and deviation of gear are generated.

Taking one new type crane reducer with two supporting points as the research object,the three-dimensional model of reducer is established by using SolidWorks,and the virtual prototype is established by importing the 3D model into the mechanical dynamics simulation software ADAMS. In order to ensure the accuracy of the simulation model,the virtual prototype model is analyzed by the contact force constraint,the angular velocity characteristic curve and the gear meshing force variation curve of each drive shaft are obtained. The simulation of the actual value and the theoretical calculation results are compared and found that the transmission shaft angular velocity and the actual the transmission error value in 0. 17%,engaging in 4% errors are very small,so the simulation model is correct. The research results provide data support for calculate gear strength and fatigue life more accurately.

The gearbox of rack test for the Three Gorges ship lift is low speed heavy duty four stages transmission,and need frequent fast reversing operation in the process of test,due to the influence of the gear meshing backlash,elastic torsional deformation of shaft and elastic deformation of gear tooth and other factors,the operation performance of gearbox will be changed during reversing process,especially the output speed and torque. In order to analyze the influence on the transmission performance of gearbox,the calculation models of the influence of the gear meshing backlash and the elastic torsional deformation of the shaft on the rotational speed are setup respectively,the output speed of the gearbox in the reversing process is calculated and compared with the output speed of gearbox measured by experiment,which verifies the accuracy of the calculation model and the test data.

The background and significance of gear test detection platform and basic database construction are introduced,and a structural scheme of bevel gear closed power flow durability test bench including the composition and system function is proposed. The 3 D model of constant speed cylindrical gearbox is established by using Solid Works 3 D software,the statics and modal of the box are analyzed according to the actual working load of the test bench by finite element method. The maximum stress,deformation and natural frequency of the box and the corresponding vibration mode are obtained,and the result of the strength check of meshing gears verify the constant speed cylindrical gearbox meeting design requirement.

Taking a high- speed motor train unit transmission gear system as an example,by using gear analysis software KISSsoft,the deformation of gear supporting axial in the transmission process is calculated.Through the method of modification to compensate the influence of the shaft deformation on the gear meshing performance. Then,the difference between before and after the modification of gear meshing contact spot,tooth surface line load distribution and the transmission error,etc are compared to ensure the motor train unit gear transmission system working more stable and reliable. The work of the research has important reference value to the design of the motor train unit gear pair.

Taking designed labyrinth seal of a high speed EMU gearbox as the research object. The numerical simulation of the internal flow field of labyrinth seal is carried out by using the Fluent software,the pressure,speed,velocity vector and turbulence distribution cloud of the internal flow field of the labyrinth seal are obtained. The sealing mechanism and process of the gearbox labyrinth seal is analyzed. The results show that the fluid flows through the sealing gap when the pressure is reduced,the pressure is reduced very little.When the fluid flows out of the sealing gap into the cavity is the pressure equalizing process. After entering the cavity,the turbulivity of the cavity is the largest and the pressure is the smallest. As the distance from the center of the cavity increases,the speed increases and the pressure increases. The distribution characteristics of the flow field in the labyrinth seal under different pressure ratios are analyzed,which indicated that the leakage increases with the increase of the inlet/outlet pressure ratio,and the pressure ratio is not linearly related to the leakage. The simulation results can be used as reference for the design of gearbox labyrinth seal.

Reducer is the key component of hoisting equipment,and the case is the carrier of the gear system and plays the role of support and fixation. The three-dimensional finite element model of the gearbox is established by Solid Works software and imported it into ANSYS Workbench. The statics analysis is accomplished for each actual loading condition,the changing curve of the maximum stress and the deformation is obtained,the analysis results can provide the data support for the subsequent structure improvement and light-weight design. The natural frequency and vibration type is obtained by completing the modal analysis of the case,and whether the resonance phenomenon happens can be determined by comparing the natural frequency of the reducer with the meshing frequency and the rotational frequency.

Through the analysis of the influence factors on transmission efficiency of gearbox,a theoretical analysis model of gearbox transmission efficiency is set up from the power consumption,and the influences of gear meshing loss,bearing friction loss,oil loss,oil seal friction loss and windage loss on gearbox transmission efficiency are considered. The analysis model is validated according to the test data of a low speed and heavy duty gearbox,and the influences of speed and torque on the transmission efficiency of gearbox are discussed,the changing curves of gear efficiency with the rotational speed and torque are obtained,the foundation for further research on the efficiency of the gearbox is laid.

In the case of dry friction,the stress value and distribution on and under contact surface of gear and rack are analyzed in terms of elasticity theory,the results show that the maximum shear stress moves to the tooth surface with the increase of friction factor,and the maximum shear stress mostly occurs on the nether boundary point of single tooth mesh area of the gear.

Based on a typical component in the large crane reducer as the object,a three-dimensional tolerance model is established.Through sensitivity numeric analysis,the critical and non-critical dimensions influencing the assembly requirements can be found out,the reasonable distribution of each component tolerances can be achieved,which lays a basis for the optimization of components accuracy design.