As urbanization accelerates and the number of high-rise buildings continues to grow, elevators, as core equipment for vertical transportation, are finding increasingly widespread application. According to industry statistics, there are nearly 1,000 elevator manufacturers in my country, and market competition is intensifying. Reducing costs and increasing efficiency through product optimization has become a key issue for the industry. Traction elevators, as the mainstream type of elevator, have matured their supporting technology after a century of development. Their structure consists of eight major systems: the traction system, the car system, and the guide system. The car system directly bears the load, while the car frame, as the structural framework of the car, has a design that directly impacts the elevator's safety performance and manufacturing cost. Excessive car frame mass can lead to material waste and redundant design; while too light a weight can fail to meet load requirements, posing a safety hazard.
We conducted optimization research on the traction elevator car frame structure, using numerical simulation software to analyze the statics and dynamics of the frame. This approach allows us to achieve a lightweight design while ensuring structural safety, providing a practical solution for improving economic efficiency for enterprises.
1. Elevator Car Frame Mechanical Analysis: The Basis of Optimization Design
To ensure the scientific and reliable optimization solution, the research team first used professional numerical simulation software to conduct a comprehensive analysis of the mechanical properties of the elevator car frame under different operating conditions, providing data support for subsequent lightweight design.
1.1 Static Analysis: Stress Performance under Rated and Overload Conditions
The static analysis focused on the rated operating conditions and extreme overload conditions of normal elevator operation. Its core objective was to simulate the stress distribution and displacement of the car frame by establishing a precise structural model. During the research, the team first constructed a 3D structural model of the car frame using SolidWorks software and then imported the model into Abaqus analysis software in x_t format. Given the complex structure of the car frame, to simplify the calculations and maintain analysis accuracy, they omitted small details such as connections, welds, bolts, and chamfers. The main structure was then converted into a shell, and components such as the return pulley, safety clamp, and guide shoe were simplified to rigid bodies. The parameter settings were based on actual elevator operating standards, with a traction motor power of 11.7kW, a car weight of 1100kg, a rated speed of 1.75m/s, a rated load of 1050kg, and a lifting height of 82.5m. Horizontal constraints were applied to the model to simulate the actual weight, car pressure, and load pressure borne by the car frame. S4R elements were used for meshing, with a mesh size of 10mm, resulting in 590,350 nodes and 431,287 elements, ensuring model accuracy.
Analysis results show that under rated operating conditions, the maximum stress in the car frame is 138.9MPa, far below the material yield stress. The maximum stress occurs at the contact between the anti-vibration rubber and the car frame side beams, resulting in a localized stress concentration due to contact compression. However, this concentrated area only covers two mesh elements and has minimal impact on the overall stress of the car frame. Calculations show that the ratio of the material's yield stress to a 1.5 times safety factor is 156.7 MPa (235 MPa/1.5), and the maximum stress of 138.9 MPa meets safety requirements.
Under a 125% overload condition, the maximum stress in the car frame rises to 296.2 MPa, again concentrated at the contact point between the anti-vibration rubber and the car frame side beams. The stress concentration area expands to four grid cells, but its impact on the overall structural stress is still limited. Aside from the stress concentration area, the maximum stress in the remaining areas is 166.4 MPa. While lower than the material's yield strength, it falls short of the 1.5 times safety factor requirement. Furthermore, the maximum cumulative displacement of the car frame is 9.5 mm, necessitating the avoidance of long-term overload operation in actual use.
1.2 Dynamic Analysis: Verifying Structural Safety Under Extreme Operating Conditions
The dynamic analysis focuses on extreme risk conditions during elevator operation-car bottoming and emergency braking. Under these conditions, the car frame's velocity and acceleration change dynamically over time. Transient dynamic simulations are performed using the Abaqus Explicit module. The initial velocity is the contact velocity between the buffer and the car frame, and the amplitude of the actual velocity change during operation is input to simulate the dynamic stress response of the structure.
The simulation results show that when the car bottoms out, large stress concentrations occur at the contact point between the buffer and the car frame, and some components undergo plastic deformation due to excessive stress. At 0.084 seconds after bottoming out, the maximum stress at the impact point reaches 248.2 MPa. While this does not exceed the material's strength limit of 400 MPa and prevents overall structural failure, the car frame loses its ability to operate normally. Therefore, comprehensive safety protection systems are essential in elevator design and operation to prevent car bottoming. Under emergency braking conditions, the maximum stress value of the car frame is 229.1MPa, which is lower than the yield stress of the material, and the stress action range is small, which will not pose a threat to the structural safety. This shows that the elevator's emergency braking system can effectively ensure the stability of the car frame structure.
2. Optimization Design of the Upper Crossbeam of the Car Frame: A Lightweight Solution in Action
Based on mechanical analysis results, the research team found that the overall stress of the car frame met safety requirements and had significant safety margins during normal operation, indicating potential for lightweight optimization. Further analysis of the stress distribution of each component identified the upper crossbeam as the core optimization target-its stress values under various operating conditions were well below the material limit, indicating the greatest optimization potential.
2.1 Determination of Optimization Variables and Methods
Considering the stability of the overall structural layout of the car frame, we decided not to change key dimensions such as the length, bend height, and overall height of the upper crossbeam. We focused solely on the upper crossbeam thickness as the sole optimization variable to avoid affecting the stress balance of other components due to structural adjustments. The optimization method employed a "step-by-step reduction" approach, starting with an original thickness of 6mm and reducing the thickness by 0.5mm at a time. Through multiple simulation analyses, we verified the stress performance and safety status of the upper crossbeam with varying thicknesses, ultimately selecting the optimal solution.
2.2 Performance and Quality Comparison Before and After Optimization
Multiple rounds of simulation verification confirmed that reducing the upper crossbeam thickness from 6mm to 4mm achieved the optimal balance between structural performance and lightweighting. In terms of stress performance, the maximum stress of the upper crossbeam before optimization was only 17.08MPa, well below the material yield strength. After optimization, the maximum stress increased to 139.5MPa, still below the safety threshold of 156.7MPa, meeting the 1.5x safety factor requirement and demonstrating stable and reliable mechanical properties.
In terms of lightweighting and cost control, after optimization, the mass of a single upper crossbeam was reduced from 29.95kg to 22.46kg, a weight reduction of 7.49kg per beam, and a lightweighting degree of 25%. The reduced mass of the upper crossbeam also indirectly reduces the overall load-bearing load of the car frame, further optimizing the stress state of the entire car system, forming a virtuous cycle of "lightweight - low load - greater safety".
3. Research Conclusions and Industry Value
This research on the optimized design of the traction elevator car frame structure, through scientific mechanical analysis and precise parameter optimization, yielded the following key conclusions: First, the maximum stress in the car frame under rated operating conditions was 138.9 MPa, and the maximum stress in non-concentrated areas under overload conditions was 166.4 MPa, both meeting basic mechanical requirements. Second, the structure did not suffer overall damage under car bottoming and emergency braking conditions, but the risk of car bottoming remains a concern. Third, by optimizing the upper crossbeam thickness from 6mm to 4mm, safety performance was maintained while achieving a 25% lightweighting goal.
From an industry perspective, this research provides elevator manufacturers with a practical cost-saving and efficiency-enhancing solution. By reducing the upper crossbeam thickness, manufacturers can directly reduce the use of raw materials such as steel, thereby lowering production costs. Furthermore, the lightweight car frame reduces energy consumption during elevator operation, improving the overall energy efficiency of the equipment. In addition, the "mechanical analysis - variable screening - step-by-step optimization" method used in the research also provides a reference paradigm for the optimized design of other structural components in the elevator industry, promoting the industry's transformation from "empirical design" to "data-driven design", and helping elevator products achieve a higher level of balance between safety and economy.
