Topological optimization design method for improving vibration fatigue strength of automobile electric compressor bracket

Abstract

The invention discloses a topological optimization design method for improving the vibration fatigue strength of an automobile electric compressor support. The method comprises the steps that a topological optimization finite element model is established; carrying out topological optimization space partitioning; setting topological optimization parameters; topological optimization calculation is implemented; correcting the three-dimensional model of the compressor bracket; and simulating and checking the compressor bracket structure. According to the method, the overall design area of the compressor bracket is subjected to topological optimization by adopting a pseudo-density theory method, the casting draft direction and the assembly process are considered, a dual algorithm of topological optimization numerical simulation is adopted, multiple iterative calculations are performed, and the vibration fatigue strength of the optimized compressor bracket is checked, so that the reliability of the compressor bracket is improved. The method has the advantages of being simple, reliable, practical and the like, and has very high practical value and popularization value in the technical field of automobile electric compressor support optimization.

Description

Technical Field

[0001] The invention relates to the field of automobile air-conditioning electric compressors, and in particular to a topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket. Background Art

[0002] The automotive air conditioning compressor is an important component of the automotive air conditioning refrigeration system, which plays the role of compressing and transporting refrigerant vapor. The compressor and the engine are prone to resonance at a certain speed, and the vibration and noise generated will make the car occupants feel uncomfortable. The air conditioning compressor bracket is an important way to solve the vibration transmission of the compressor. New energy vehicles generally use motor-driven compressors. The electric compressor of hybrid models is integrated with the engine and drive motor. The vibration excitation is complex, so it is very necessary to improve the vibration fatigue strength of the compressor bracket.

[0003] If the compressor bracket structure is improperly designed, it may lead to insufficient strength problems such as fracture. Too low vibration fatigue strength may also cause damage due to structural resonance.

[0004] CN113139237A discloses a topology optimization method for improving the mode of an automobile air-conditioning compressor bracket: constructing a three-dimensional assembly model of a compressor system, a compressor bracket and a power assembly, and performing structural dispersion and meshing on the three-dimensional assembly model; obtaining material properties of the compressor system, the compressor bracket and the power assembly; constructing and dividing the design area and the non-design area of ​​the compressor bracket; using the relative density of the unit as a topology design variable, and using the SIMP algorithm to perform topology optimization on the design area of ​​the compressor bracket; applying boundary conditions, obtaining optimization variables, constraints and optimization targets; using a relative density topology optimization algorithm and performing multiple iterative calculations to obtain a topologically optimized compressor bracket; correcting the topologically optimized compressor bracket, and obtaining a three-dimensional model of the optimized compressor bracket.

[0005] However, the above patent only performs topological optimization on the local structure of the compressor bracket, does not perform forward design from the overall structure, and does not provide an optimization method for improving vibration fatigue strength, so there is still a risk of vibration fatigue damage.

[0006] Therefore, in order to improve the vibration fatigue strength of the compressor bracket and optimize the compressor bracket structure, a new design idea and method is needed. Summary of the invention

[0007] In order to solve the above problems existing in the prior art, the present invention provides a topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket, adopts a pseudo-density theory method to perform topology optimization on the overall design area of ​​the compressor bracket, considers the casting demolding direction and the assembly process, adopts a dual algorithm of topology optimization numerical simulation and performs multiple iterative calculations, and performs vibration fatigue strength verification on the optimized compressor bracket. The present invention has the advantages of simplicity, reliability, and practicality, and has high practical value and promotion value in the technical field of automobile electric compressor bracket optimization.

[0008] The objective of the present invention is achieved through the following technical solutions:

[0009] A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket comprises the following steps:

[0010] S1. Create a topology optimized finite element model;

[0011] S2. Topology optimization space partitioning;

[0012] S3. Topology optimization parameter setting;

[0013] S4. Implement topology optimization calculations;

[0014] S5. Modification of the three-dimensional model of the compressor bracket;

[0015] S6. Simulation verification of compressor bracket structure.

[0016] Further, the step S1 comprises:

[0017] A three-dimensional assembly model of the electric compressor assembly, compressor bracket and powertrain is established, a design space model of the electric compressor bracket is constructed, and the three-dimensional assembly model is structurally meshed to obtain the material properties of the electric compressor assembly, compressor bracket and powertrain, the weight, center of mass coordinates, and moment of inertia of the compressor assembly.

[0018] Further, the step S2 comprises:

[0019] Construct and divide the global design space into design area and non-design area, where the design area is the area for topology optimization.

[0020] Furthermore, in step S2, the optimized design area is divided into a forward draft area and a reverse draft area; the non-design area includes an assembly bolt through hole and an assembly concave platform area.

[0021] Furthermore, the step S3 includes: applying boundary conditions, obtaining optimization design variables, constraint conditions and optimization objectives.

[0022] Furthermore, in step S3, the optimization design variables include minimum member size, maximum member size, and demolding direction; the constraints include first-order constraint modal frequency and volume ratio; the optimization target position has the minimum weight; the first-order constraint modal frequency limit is f≥(2nZ) / (60r), n is the maximum engine speed, Z is the number of cylinders, and r is the number of engine strokes.

[0023] Furthermore, in step S4, the pseudo-density of the unit is used as the topological design variable, and the SIMP algorithm is used to perform topological optimization on the design area of ​​the compressor bracket; the dual method is used and multiple iterative calculations are performed to obtain the topological structure of the compressor bracket after topological optimization.

[0024] Furthermore, the step S5 includes: performing structural correction on the compressor bracket after topology optimization to obtain a three-dimensional model of the optimized compressor bracket.

[0025] Further, the step S6 includes: using a random vibration simulation method to calculate the random vibration stress response of the compressor bracket, and calculating the random vibration stress response of the compressor bracket according to the excitation PSD and the structural transfer function.

[0026] Further, in step S6, the calculation method of the random vibration stress response is as follows:

[0027]

[0028] In the formula, S r (f) is the random vibration stress response, H is the transfer function, S i (f) is the random excitation PSD.

[0029] Compared with the prior art, the present invention has the following improvements:

[0030] The present invention adopts the pseudo-density theory method to perform topological optimization on the overall design area of ​​the compressor bracket, taking into account the casting demolding direction and the assembly process. The advantage of the present invention is that not only the force transmission path structure of the compressor bracket is determined in the conceptual scheme, but also the structural detail design such as casting processing and assembly space is taken into account.

[0031] The present invention adopts the dual algorithm of topology optimization numerical simulation and performs vibration fatigue strength verification on the optimized compressor bracket after multiple iterative calculations. The advantage is that the bracket is light in weight, has good formability and assembly properties, and meets the vibration fatigue strength requirements of the compressor bracket while meeting the performance requirements.

[0032] In summary, the present invention has the advantages of simplicity, reliability, and practicality, and has high practical value and promotion value in the technical field of automobile electric compressor bracket optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings required for use in the embodiment are briefly introduced below.

[0034] Figure 1 It is a schematic diagram of the structure of the grid model of the electric compressor assembly described in an embodiment of the present invention.

[0035] Figure 2 It is a schematic diagram of the designed space and non-designed space (including the demoulding direction and the assembly concave structure) of the compressor bracket described in the embodiment of the present invention.

[0036] Figure 3 This is a diagram of the optimized structure of the compressor bracket described in an embodiment of the present invention.

[0037] Figure 4 It is a schematic diagram of the modified structure of the compressor bracket described in an embodiment of the present invention.

[0038] Figure 5 This is a flow chart of a topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket according to an embodiment of the present invention.

[0039] Figure 6 This is a flowchart of obtaining optimization variables, constraints and optimization targets in the third step described in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of this application clearer, the present invention is further described below in conjunction with the accompanying drawings and embodiments, and the embodiments of the present invention include but are not limited to the following embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0041] Example

[0042] like Figures 1 to 4 As shown, this embodiment starts from the force transmission path and combines the structural deformation position and energy distribution, etc., and proposes a topology optimization design method for improving the vibration fatigue strength of the automobile electric compressor bracket, such as Figure 5 As shown, the following steps are included:

[0043] The first step is to create a topology optimized finite element model:

[0044] A three-dimensional assembly model of the electric compressor assembly, compressor bracket and powertrain is established, a design space model of the electric compressor bracket is constructed, and the three-dimensional assembly model is structurally meshed to obtain the material properties of the electric compressor assembly, compressor bracket and powertrain, the weight of the compressor assembly, the center of mass coordinates, the moment of inertia and other parameters.

[0045] The second step is topological optimization space partitioning:

[0046] The design area and non-design area of ​​the global design space are constructed and divided, and the optimized design area is the area for topology optimization.

[0047] Among them, the optimized design area can be divided into two parts: the forward draft area and the reverse draft area.

[0048] The non-designed areas include assembly bolt holes and assembly recessed platform areas.

[0049] The third step is to set topology optimization parameters:

[0050] Apply boundary conditions to obtain optimization design variables, constraints and optimization objectives.

[0051] Among them, Figure 6 As shown, the optimization design variables include the minimum member size, the maximum member size, and the draft direction. The constraints include the first-order constraint modal frequency and volume ratio. The optimization target is the minimum weight. The first-order constraint modal frequency limit is f≥(2nZ) / (60r), n is the maximum engine speed, Z is the number of cylinders, and r is the number of engine strokes.

[0052] In this embodiment, the draft size is greater than 3 times the unit size, the draft size is less than 6 times the unit size, the draft direction is two unidirectional draft controls (i.e., one forward draft and one reverse draft), the constraint function is that the first-order modal frequency is greater than 200 Hz, and the objective function is minimum weight.

[0053] The fourth step is to implement topology optimization calculation:

[0054] The pseudo-density of the unit is used as the topological design variable to carry out topological optimization of the design area of ​​the compressor bracket. The dual method is used and multiple iterative calculations are performed to obtain the topological structure of the compressor bracket after topological optimization.

[0055] Specifically, the pseudo-density of the unit is used as the topological design variable, and the SIMP algorithm is used to perform topological optimization on the design area of ​​the compressor bracket. In this embodiment, a hypothetical material with a variable relative density between 0 and 1 is introduced, namely, the pseudo-density topological optimization method. Among them, the more commonly used model is the SIMP (solid isotropic microstructure with penalization) method. When optimizing, the pseudo-density of the unit is used as the topological design variable, so that the structural topological optimization problem is converted into the optimal distribution problem of the material, which is also the most widely used topological optimization method at present. When optimizing, the pseudo-density of the unit is used as the topological design variable, so that the structural topological optimization problem is converted into the optimal distribution problem of the material.

[0056] The topology optimization iterative convergence calculation uses the relative density topology optimization algorithm and multiple iterative calculations to obtain the topology optimized compressor bracket. The dual method is used for numerical convergence iterative calculation of topology optimization, where the entity unit discrete parameter is 3 and the entity unit topology optimization checkerboard control parameter is 1. The iterative convergence tolerance of the structural mesh for multiple iterations is 0.001, and the iteration step is 0.5.

[0057] Iterative calculation is to calculate the bracket modal under given constraints. In order to be greater than 200Hz as much as possible and to keep the bracket weight as small as possible, multiple iterative calculations are required during the bracket frequency calculation process to finally obtain the optimal bracket result after topology optimization. In post-processing, the unit density threshold is generally set to about 0.2 to 0.3. Figure 3 This is the topology optimization result when the unit density is 0.3.

[0058] Step 5: Modify the 3D model of the compressor bracket:

[0059] The compressor bracket after topology optimization is structurally modified to obtain a three-dimensional model of the optimized compressor bracket.

[0060] Step 6: Simulation and verification of compressor bracket structure:

[0061] Perform random vibration simulation analysis on the compressor bracket structure and verify the vibration strength of the compressor bracket.

[0062] Specifically, the random vibration simulation method is used to calculate the random vibration stress response of the compressor bracket, and the random vibration stress response of the compressor bracket is calculated based on the excitation PSD and the structural transfer function. The calculation method of the random vibration stress response is as follows:

[0063]

[0064] Where: S r (f) is the random vibration stress response, H is the transfer function, S i (f) is the random excitation PSD.

[0065] Furthermore, the compressor bracket topology is constructed using the OSSmooth tool, and the finite element plane elements are converted into model files in formats such as IGES, on which the detailed structural design is carried out.

[0066] Through the above method, the mode of the compressor bracket optimized in this embodiment is 224 Hz, and the weight is only 0.53 kg. Both the mode and the strength meet the performance requirements, which reduces the weight of the compressor bracket and reduces the material cost.

[0067] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any changes made by adopting the design principles of the present invention, which are equivalent to adopting the key control parameters of the present invention, and non-creative labor based on these changes should fall within the scope of protection of the present invention.

Claims

1. A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket, characterized in that: The following steps are involved: S1. Create a topology optimized finite element model; S2. Topology optimization space partitioning; S3. Topology optimization parameter setting; S4. Implement topology optimization calculations; S5. Modification of the three-dimensional model of the compressor bracket; S6. Simulation verification of compressor bracket structure.

2. A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket as claimed in claim 1, characterized in that: The step S1 comprises: A three-dimensional assembly model of the electric compressor assembly, compressor bracket and powertrain is established, a design space model of the electric compressor bracket is constructed, and the three-dimensional assembly model is structurally meshed to obtain the material properties of the electric compressor assembly, compressor bracket and powertrain, the weight, center of mass coordinates, and moment of inertia of the compressor assembly.

3. A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket as claimed in claim 1, characterized in that: The step S2 comprises: Construct and divide the global design space into design area and non-design area, where the design area is the area for topology optimization.

4. A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket as claimed in claim 3, characterized in that: In step S2, the optimized design area is divided into a forward draft area and a reverse draft area; the non-design area includes an assembly bolt through hole and an assembly concave platform area.

5. A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket as claimed in claim 1, characterized in that: The step S3 includes: applying boundary conditions, obtaining optimization design variables, constraint conditions and optimization objectives.

6. A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket as claimed in claim 1, characterized in that: In step S3, the optimization design variables include the minimum member size, the maximum member size, and the demolding direction. The constraints include the first-order constraint modal frequency and the volume ratio. The optimization target position has the minimum weight. The first-order constraint modal frequency limit is f≥(2nZ) / (60r), n is the maximum engine speed, Z is the number of cylinders, and r is the number of engine strokes.

7. A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket as claimed in claim 1, characterized in that: In the step S4, the pseudo density of the unit is used as the topological design variable, and the SIMP algorithm is used to perform topological optimization on the design area of ​​the compressor bracket; the dual method is used and multiple iterative calculations are performed to obtain the topological structure of the compressor bracket after topological optimization.

8. A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket as claimed in claim 1, characterized in that: The step S5 includes: performing structural correction on the compressor bracket after topology optimization to obtain a three-dimensional model of the optimized compressor bracket.

9. A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket as claimed in claim 1, characterized in that: The step S6 includes: using a random vibration simulation method to calculate the random vibration stress response of the compressor bracket, and calculating the random vibration stress response of the compressor bracket according to the excitation PSD and the structural transfer function.

10. A topology optimization design method for improving the vibration fatigue strength of an automobile electric compressor bracket as claimed in claim 9, characterized in that: In step S6, the calculation method of the random vibration stress response is as follows: In the formula, S r (f) is the random vibration stress response, H is the transfer function, S i (f) is the random excitation PSD.

Images