An optimization method based on universal joint products

Abstract

The present invention discloses an optimization method based on a universal joint product, belonging to the technical field of universal joint coupling products. The method of the present invention comprises the steps of: S1, constructing a product parameterized model of the universal joint; S2, assembling the universal joint product; S3, optimizing the model: optimizing non-critical parts and refining critical areas; S4, analyzing stress in actual working conditions: optimizing product parameters and structure according to stress distribution, strain conditions, and displacement size in the analysis results; S5, comparing safety factor requirements according to strain distribution and strain size. If the requirements are not met, optimizing the critical areas, and recalculating stress distribution and size until the safety factor requirements are met. By establishing a parameterized model according to actual working conditions and customer needs, and optimizing the structure of the universal joint product according to stress distribution, the optimized universal joint meets the safety performance requirements, and can effectively reduce the consumption of the universal joint product by sliding friction, thereby increasing its service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of universal shaft coupling products, and more specifically, relates to an optimization method based on universal shaft products. Background Art

[0002] The existing universal joint product design is generally based on the drawings and tolerance requirements provided by the customer, creating CAD drawings or models, and processing products according to the drawings. The product life cycle and performance are determined based on experience.

[0003] One method is to use physical experiments to test its basic performance, and then design and produce universal joints based on the experimental data and working conditions. However, this method has high labor and material costs, a long design and production cycle, and poor returns.

[0004] When the finite element method is currently used to analyze universal joint products, the methods and processes rely more on personal experience, and the product operating data cannot be linked to the actual model, resulting in inaccurate analysis results.

[0005] To address the above issues, a search revealed patent CN113268831A, which discloses an analytical method for obtaining harmonic gear transmission stresses. The method involves simplifying the model created in 3D software and using hexahedral mesh elements to perform finite element meshing on the assembly model. The inp format mesh model is imported into ABAQUS, and material properties are assigned to the components. The analysis steps and analysis process output items are set. Contact interactions are defined on the mesh assembly model, and loads and boundary constraints are applied. The calculated and displayed data is then analyzed, and the stress, strain, and other data for the unit integration point of the harmonic gear at a specific incremental step within a specific analysis step are extracted from the analysis results. However, this method considers the transmission stress of the harmonic gear, which is different from the rotational stress of the universal joint.

[0006] Patent CN112487564A discloses a method for optimizing the design of a turntable baseplate, which includes the following steps: A. Disassembling and simplifying the overall turntable structure to extract the turntable baseplate structure and the turntable rotary motion unit it supports; B. Expanding the structural volume of the turntable baseplate structure based on its range of motion and non-interference space and filling it with solid material to define it as a design domain; C. Importing the design domain and the simplified three-dimensional model of the turntable rotary motion unit into finite element software, performing finite element meshing and boundary condition loading on each three-dimensional model; D. Performing a multi-condition integrated analysis within the finite element model that takes into account changes in posture; E. Establishing a topology optimization mathematical model and optimizing it using an optimization algorithm to extract a conceptual design diagram of the turntable baseplate structure. Although the turntable baseplate is rotationally connected, its surface is uniformly stressed, without excessive stress concentrations.

[0007] The product structures in the above patents are different from universal joints. Universal joints include a flange fork and a cross shaft assembled in the flange fork. There are multiple stress concentration points on the surface of the universal joint. How to optimize the stress concentration points of the universal joint product and thus improve its safety in use is an urgent problem to be solved. Summary of the Invention

[0008] 1. Problem to be solved

[0009] In order to solve the problem that stress concentration in existing universal joint structures affects the safety of use, the present invention provides an optimization method based on universal joint products, and the optimized universal joint products meet the safety performance of use.

[0010] 2. Technical solution

[0011] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0012] The present invention provides an optimization method based on a cardan shaft product, comprising the steps of:

[0013] S1. Build a product parametric model of a universal joint, wherein the universal joint includes a flange fork and a cross shaft assembled in the flange fork;

[0014] S2. Assemble universal joint products: establish digital models, perform physical simulation motion, and simulate assembly;

[0015] In this step, ensure that the cross shaft passes through the center of the universal joint smoothly. If there is interference, fix it by revising the parameters.

[0016] Among them, the design method of the assembly route is: move the cross shaft to the upper end of the flange fork, select one of the shaft diameters to penetrate into the flange fork bearing position, so that the cross shaft shaft diameter radius is close to the inside of the flange fork bearing hole, and the other side of the cross shaft shaft diameter is adjusted left and right to the middle position of the upper part of the flange fork, press it to pass through the flange fork bearing position, and finally adjust the cross shaft to the middle position of the flange fork.

[0017] S3. Optimize the model: optimize non-critical parts and refine key areas;

[0018] S4. Analyze stress in actual working conditions: Optimize product parameters and structure based on stress distribution, strain, and displacement in the analysis results. Actual working conditions include adding actual torque, friction coefficient, and contact relationship.

[0019] S5. Compare the strain distribution and strain size with the customer's safety factor requirements. If they do not meet the requirements, optimize the key areas and recalculate the stress distribution and size until the customer's safety factor requirements are met.

[0020] Specifically, the optimization steps include: step S.1 importing the numerical model and meshing it using tetrahedral meshing;

[0021] A cross-axle universal joint consists of a flange fork and a cross-axle assembled in the flange fork. During use, the cross-axle rotates to drive the flange fork. Due to the complex structure of the product, stress distribution is uneven. Especially in cases of large deviation angles and high torque transmission, stress concentration areas are prone to deformation or even fracture. Therefore, this application uses a 3D tetrahedron mesh for the general parts of the universal joint and a 2D tetrahedron mesh for key areas. The key areas are stress concentration areas, such as the cross-axle, where the stress concentration areas are the fillet of the cross-axle journal, and the flange fork, where the stress concentration areas are the bottom recess and fillet of the flange fork.

[0022] Surprisingly, it was found that the optimization method of the present invention can not only optimize the stress concentration of the product to meet the safety factor, but also improve the uniformity of the force on the surface of the optimized product, effectively reducing the wear of the product caused by friction. During use, the cross shaft and the flange fork will not only generate stress caused by surface contact, but also sliding friction. In order to reduce the friction between the contact surfaces, grease is often added when using a universal joint. The distribution of grease is related to the surface properties. Grease is unevenly distributed on uneven surfaces, and the wrapping effect is poor. This application optimizes the surface flatness while optimizing the surface stress. The optimized universal joint product has a more uniform surface force, and a product with uniform and consistent lubricant wrapping is obtained, thereby reducing friction and increasing service life.

[0023] In addition, the operating environment of the universal joint is a high-temperature water vapor environment, especially under high-temperature hot rolling conditions of 850℃~1000℃. Water vapor condenses and accumulates on the surface of the product, which is more prone to wear and even rust under long-term friction. By optimizing the product structure, the condensation of water vapor on the product surface can be reduced, thereby improving the service life of the universal joint.

[0024] Steps S1-S2 may be performed using three-dimensional modeling design software; and step S3 may be performed using software capable of mechanical analysis.

[0025] Compared to existing technologies, the present invention provides an optimization method for universal joint products that features a novel design, rational structure, ease of implementation, and excellent results. Based on actual operating conditions and customer needs, a parametric model is established, followed by physical simulation to ensure the accuracy and rationality of the flange yoke and cross shaft designs, thus reducing design cycles. Simultaneously, stress analysis is performed on the parametric model, avoiding multiple physical experiments and saving costs. Furthermore, the structure of the universal joint product is optimized to ensure its functionality and extend its lifespan, providing an analytical basis for universal joint products. Through design optimization, the present invention is applicable to product structures of varying specifications, is simple and easy to implement, and offers high versatility and practicality.

[0026] The universal joint optimization method of the present application can be used for cross-axis universal joint couplings, including BH type (standard telescopic welding type), BF type (standard telescopic flange type), DH type (short telescopic welding type), CH type (long telescopic welding type), WH type (non-telescopic welding type), WF type (non-telescopic flange type), and WD type (non-telescopic short type).

[0027] 3. Beneficial effects

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention provides an optimization method based on a cardan shaft product, establishes a parameterized model, optimizes the cardan shaft product structure according to the stress distribution, and the optimized cardan shaft meets the safety performance requirements;

[0030] (2) The present invention provides an optimization method based on a universal joint product, which divides the universal joint model into a network by region, focuses on optimizing key areas where stress is concentrated, effectively reduces the consumption of the universal joint product caused by sliding friction, and improves its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise specified, these drawings are intended only to conceptually illustrate the structures described herein and are not necessarily drawn to scale.

[0032] Figure 1-3 This is a schematic diagram of the derivation process of the cross shaft journal fillet size;

[0033] Figure 4 This is a schematic diagram of the structure of the universal joint product of the present invention;

[0034] Figure 5 This is a diagram showing the cross shaft simulating entry into the interior of the flange fork in the present invention, with the two arrows in the diagram indicating the assembly routes;

[0035] Figure 6 This is the optimized structural diagram of the universal joint product in the present invention;

[0036] Figure 7 This is a stress distribution diagram of the active end flange fork in the universal joint product of the present invention;

[0037] Figure 8 This is the strain distribution diagram of the cross shaft in the universal joint product of the present invention;

[0038] Figure 9 This is the cross shaft displacement diagram of the universal joint product of the present invention. DETAILED DESCRIPTION

[0039] The following detailed description of exemplary embodiments of the present invention refers to the accompanying drawings, which form a part of the description, and in which exemplary embodiments of the present invention that can be implemented are shown as examples. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but is merely for illustration and does not limit the description of the features and characteristics of the present invention, so as to propose the best way to perform the present invention and be sufficient to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0040] This invention provides an optimization method for cardan shaft products. Based on actual operating conditions and customer requirements, a parametric model is established. Based on this parametric model, physical simulation is first performed to ensure the accuracy of actual parameters. Finite element analysis is then performed to optimize the product and performance to meet actual usage requirements. This method effectively solves existing problems in cardan shaft design optimization and production assembly.

[0041] The steps of three-dimensional modeling and mechanical analysis in the embodiment of the present invention refer to patent CN112487564A, and are improved based on the universal joint.

[0042] Example 1

[0043] A universal joint includes a flange fork and a cross shaft assembled in the flange fork. Example 1 provides an optimization method for a universal joint product, including establishing a parametric model of the universal joint product, first performing physical simulation based on the parametric model to ensure that the cross shaft is installed inside the flange fork, then performing finite element analysis of key areas based on the parametric model, and continuously optimizing the product structure based on the results. Specifically, the method includes the following steps:

[0044] The present invention provides an optimization method based on a cardan shaft product, comprising the following steps:

[0045] Step 1: According to the actual working conditions of the product and customer requirements, sort out the boundary parameters. The actual working condition coefficient K in Example 1 is 1.5. The customer requirements are motor power: 400kw, motor speed: 500r / min, reduction ratio 3.5, motor output type: one-to-two, and the theoretical calculated torque of the motor is: 16.044kN·m. Set the actual boundary parameters to 16.5kN·m. Based on the boundary parameters, establish a parameterized model to ensure the correlation between the actual working conditions and the model.

[0046] Step 2: Physically inspect the cross shaft and flange yoke to ensure that the cross shaft is securely assembled into the flange yoke to avoid interference caused by design errors.

[0047] Among them, the design method of the assembly route is: move the cross shaft to the upper end of the flange fork, select one of the shaft diameters to penetrate into the flange fork bearing position, so that the cross shaft shaft diameter radius is close to the inside of the flange fork bearing hole, and the shaft diameter on the other side corresponding to the shaft neck is adjusted left and right to the middle position of the upper part of the flange fork, press it to pass through the flange fork bearing position, and finally adjust the cross shaft to the middle position of the flange fork.

[0048] Step 3: Import the flange fork and cross shaft into the mechanical analysis software to create a simplified model. In Example 1, the flange fork fillet size is adjusted to: R1 = 10mm, R2 = 5mm, and the cross shaft journal fillet radius R is 13mm. The assembled model is as follows Figure 4 As shown, the assembly path diagram is as follows Figure 5 As shown. Among them, R is the radius of the cross shaft journal fillet, R1 is the angle radius between the flange fork neck and the base, and R2 is the angle radius between the flange fork fork head and the neck, as shown Figure 1-3 shown.

[0049] Step 4: Mesh division. The flange fork adopts 3D tetrahedral mesh division, 3D body mesh: element type: CTETRA10, element size: 10mm, see Figure 5 .

[0050] The cross axis is divided into 3D tetrahedral meshes, the element type is CTETRA10, and the element size is 10mm.

[0051] For mesh refinement of the cross-shaft journal fillet area, a 2D mesh was used. Based on the model size, three layers of mesh were maintained in the fillet area. The mesh in the critical area was refined; the element size was 6 mm, and the curvature-based size variation was 20%.

[0052] For the flange fork bottom socket and fillet refinement mesh, use 2D first-order quadrilateral (CQUAD4) mesh: use 2D mapping mesh to refine the mesh of the bottom fillet area, and use the mesh control function to change the fillet radial mesh number to 3. The network division diagram is as follows: Figure 6 shown.

[0053] Step 5: Define the simulation working conditions. The material properties are shown in Table 1. Generate stress, strain, and displacement cloud maps. Based on the actual working conditions of the universal joint product and customer requirements, load the relevant torque and constraints. The cross shaft and flange fork are bonded surface to surface. One end of the flange fork is fixed, and a load of 16,500 Nm is added to the other end. If a bearing outer ring is added to the cross shaft, four contact points are set between the cross shaft and the bearing outer ring. The friction coefficient is 0.15. Contact parameters: Set clearance and penetration to zero.

[0054] Step 6: Result judgment: Open the analysis results, such as Figure 1 shown.

[0055] Table 1 Material properties of the universal joint shaft of Example 1

[0056]

[0057] The stress distribution and stress magnitude of the bottom recess and fillet of the flange fork in Example 1 are obtained:

[0058] Cross shaft material: 20CrMnTi, yield strength: σy=835MPa, maximum stress: σ=524.92MPa;

[0059] Flange fork material: 42CrMo, yield strength: σy=930MPa, the maximum stress of the active end flange fork is σ=458.38MPa, such as Figure 7 As shown;

[0060] The maximum stress of the driven end flange fork is: σ = 450.97 MPa;

[0061] Cross shaft safety factor: n = σy / σ = 1.59;

[0062] Safety factor of active end flange fork: n = σy / σ = 2.01;

[0063] Safety factor of driven end flange fork: n = σy / σ = 2.06;

[0064] Therefore, the minimum value of the safety factor is: n=1.59, and the theoretical operating safety factor is: 1.5. The calculated safety factor 1.59>theoretical safety 1.5, which meets the working condition requirements.

[0065] Step 7: Convert into boundary conditions according to actual working conditions and customer requirements, and calculate the cross-axis strain distribution and strain magnitude, such as Figure 8 As shown, according to step 6, it is calculated whether the product meets the actual usage requirements.

[0066] The following derivation is made for the determination of the cross shaft journal fillet:

[0067] like Figure 1-3 As shown, there are three contact points between the cross shaft and the flange fork, namely contact point 1, contact point 2, and contact point 3. The total length of the cross shaft is known to be L1 = 175mm, the diameter of the flange fork shaft hole is L2 = 90mm, and sinα = L2 / L1 is calculated. According to sinα = sinβ and contact point 3, a hypotenuse 2 is made. Then, a straight line 1 is made based on contact point 2 and hypotenuse 1. The intersection of straight line 1 and hypotenuse 2 is obtained, and the distance between the intersection and contact point 3 is measured: L3 = 127.4mm. L3 is the distance from the cross shaft end face to the cross shaft journal fillet. Among them, L1-L9 are intermediate parameters, see Figure 1-3 .

[0068] According to: L4 = 36.8mm, calculate L as follows:

[0069] L=L1-L3-L4=175mm-127.4mm-36.8mm=10.8mm;

[0070] According to: L1 = 175mm, L4 = 36.8mm, L = 10.8mm;

[0071] Calculation results show that: L5 = L1 / 2 - L4 - L = 39.9 mm;

[0072] According to: L5 = 39.9mm, R1 = 55mm, L8 = 64.64mm;

[0073] Using the Pythagorean Theorem: L6 2 =R12-L52, L6=37.85mm, L7=L6-L8 / 2=5.53mm;

[0074] R 2 =(R-L7) 2 +L 2 =13.31mm,

[0075] In order to avoid interference during assembly, the maximum radius of the cross shaft journal of the 225 specification can be: R = 13mm.

[0076] The final performance is shown in Table 2.

[0077] Example 2

[0078] The working conditions and steps of Example 2 are basically the same as those of Example 1, except that the initial radius of the cross shaft journal is 6 mm.

[0079] When the cross-shaft journal fillet is 6 mm, the working condition requirements and method steps are consistent with those in Example 1, and only the variable of the cross-shaft journal fillet size is changed for analysis.

[0080] The cross shaft can be smoothly assembled into the universal shaft to meet the assembly requirements.

[0081] Cross shaft material: 20CrMnTi, yield strength: σy=835MPa, maximum stress: σ=668.22MPa;

[0082] The cross shaft safety factor is obtained as follows: n = σy / σ = 1.25, 1.25 < 1.5, which does not meet the actual use requirements.

[0083] The fillet of the flange fork and the cross shaft journal in the key area are optimized, the stress distribution and size are recalculated, and the product performance is improved.

[0084] The final performance is shown in Table 2.

[0085] Example 3

[0086] The working conditions and steps of Example 3 are basically the same as those of Example 1, except that the initial radius of the cross shaft journal is 20 mm.

[0087] When the cross shaft journal radius is 20 mm, the cross shaft cannot be smoothly assembled into the universal shaft and does not meet the assembly requirements.

[0088] Cross shaft material: 20CrMnTi, yield strength: σy=835MPa, maximum stress: σ=527.89MPa;

[0089] Cross shaft safety factor: n = σy / σ = 1.58, 1.58>1.5, the safety factor meets the actual use requirements, but does not meet the assembly requirements, so it does not meet the actual use requirements.

[0090] The final performance is shown in Table 2.

[0091] Table 2 Cross shaft journal fillet size and performance of Examples 1-3

[0092]

[0093] In summary, a cross shaft journal radius of 13mm is more appropriate.

[0094] Example 4

[0095] The steps of Example 4 are basically the same as those of Example 1. The dimensions of the remaining areas are consistent with those of Example 1. The key components of the flange fork are optimized and analyzed. The original flange fork fillet 1 has a size of R1 = 10 mm and a fillet 2 has a size of R2 = 5 mm. After loading the actual working conditions, the maximum stress and safety factor are calculated and compared as follows:

[0096] The flange fork material is 42CrMo, with a yield strength of σy = 930 MPa. The maximum stress of the active end flange fork is σ = 458.38 MPa; the maximum stress of the driven end flange fork is σ = 450.97 MPa.

[0097] Safety factor of active end flange fork: n = σy / σ = 2.01; satisfying: 2.01>1.5;

[0098] Safety factor of driven end flange fork: n = σy / σ = 2.06; satisfying: 2.06>1.5;

[0099] Therefore, it meets the actual usage needs.

[0100] Example 5

[0101] The steps of Example 5 are basically the same as those of Example 1. The dimensions of the remaining areas are consistent with those of Example 1. The key components of the flange fork are optimized and analyzed.

[0102] The dimensions of the flange fork fillet in Example 5 are: R1 = 5 mm, R2 = 3 mm. The working conditions and method steps are consistent with those in Example 1. Only the variable of the flange fork fillet size is changed for analysis.

[0103] Flange fork material: 42CrMo, yield strength: σy = 930MPa, recalculated maximum stress of the active end flange fork is σ = 526.33MPa; the maximum stress of the driven end flange fork is: σ = 525.58MPa;

[0104] Safety factor of active end flange fork: n = σy / σ = 1.77; satisfying: 1.77>1.5;

[0105] Safety factor of driven end flange fork: n = σy / σ = 1.77; satisfying: 1.77>1.5;

[0106] By comparing the two data, the fillet size is modified to affect the stress of the flange fork.

Claims

1. An optimization method based on a cardan shaft product, characterized in that: Including steps: S1. Build a product parametric model of a universal joint, wherein the universal joint includes a flange fork and a cross shaft assembled in the flange fork; S2. Assemble the universal joint product. The assembly route in step S2 is designed as follows: move the cross shaft to the upper end of the flange fork, select one of the journals and insert it into the flange fork bearing position, so that the cross shaft journal fillet is close to the inner side of the flange fork bearing hole, adjust the other journal corresponding to the journal to the middle position above the flange fork, press it to pass through the flange fork bearing position, and finally adjust the cross shaft to the middle position of the flange fork. S3. Build a simplified model of the flange fork and cross shaft, and divide the model into critical areas and non-critical areas. The critical areas are stress concentration areas, including the cross shaft journal fillet area and the flange fork bottom pocket and fillet area, and are divided using 2D meshes. The remaining parts are non-critical areas and are divided using 3D tetrahedral meshes. S4. Analyze the stress distribution of the universal joint product under actual working conditions. The analysis results include: stress distribution, stress magnitude, displacement magnitude, and safety factor calculated based on stress distribution, stress magnitude, and yield strength. The actual working conditions include adding actual torque, friction coefficient, and contact relationship. S5. Optimize the model until the safety factor requirements are met: Compare the safety factor calculated based on stress distribution, stress magnitude, and yield strength with the customer's safety factor requirements. If the requirements are not met, optimize the key areas of the model and recalculate the stress distribution and stress magnitude until the customer's safety factor requirements are met.

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