Hub motor thermal coupling analysis method and system based on disc brake severe working condition and storage medium

Abstract

The invention discloses a wheel hub motor thermal coupling analysis method and system based on a disc brake severe working condition and a storage medium. A wheel hub motor model is simplified to form a simplified wheel hub motor three-dimensional model; importing the three-dimensional model of the hub motor into finite element software, performing grid division, and setting parameters to form a finite element model; the performance of the hub motor in the high-temperature running state is determined by setting brake pressure for the finite element model to carry out stress analysis under the severe working condition of the brake disc, setting angular velocity to carry out temperature analysis under the severe working condition of the brake disc and carrying out coupling analysis on stress analysis and temperature analysis results. According to the method, the finite element model of the hub motor is formed by establishing the three-dimensional model and importing the three-dimensional model into finite element analysis software, performing grid division and setting parameters, and thermal coupling analysis of the hub motor is performed by adopting the finite element model, so that the performance and the reliability of an integrated hub motor product in a high-temperature operation state can be simulated, and an optimization direction can be found.

Description

Technical Field

[0001] The present invention belongs to the field of automobile technology and relates to a joint simulation design method for the performance and reliability of a hub motor product with an integrated reducer and brake, specifically a thermal coupling analysis method, system and storage medium for a hub motor under harsh working conditions based on a disc brake. Background Art

[0002] As a new solution for efficient electrification of vehicles, the integrated hub motor with integrated reducer and brake is a hot topic in the field of vehicle research and development. The integrated hub motor with integrated reducer and brake is installed in the wheel rim of the vehicle. When running, the heat dissipation condition is poor and the temperature environment of the mechanism is very harsh.

[0003] When the vehicle brakes, the rapid mutual friction between the brake friction pairs generates a large amount of heat, causing the temperature of the brake to rise rapidly. Excessive temperature will cause the brake to decay during braking, thus affecting the braking performance of the vehicle, and will also cause thermal fatigue cracks on the surface of the brake disc, reducing its service life. At the same time, the maximum operating temperature of the motor and reducer is required to be lower than that of the brake. When the brake is in severe working conditions, the temperature of the brake is transmitted to the motor and reducer, which will also cause serious failure consequences. Therefore, it is necessary to analyze the thermal coupling of the integrated hub motor product in order to better optimize the hub motor product.

[0004] The R&D cost of integrated hub motor products is high, and the corresponding test costs are also high and the cycle is long. Due to the limitations of existing reliability design and analysis technology, it is impossible to analyze products such as integrated hub motors with integrated reducers and brakes under braking conditions. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the above-mentioned background technology and to provide a hub motor thermal coupling analysis method, system and storage medium based on the harsh working conditions of disc brakes, so as to simulate the performance and reliability of hub motor products when they are in high temperature operation state.

[0006] The technical solution adopted by the present invention is: a thermal coupling analysis method of a hub motor under severe working conditions of a disc brake,

[0007] Simplifying the wheel hub motor model to form a simplified three-dimensional model of the wheel hub motor;

[0008] Import the three-dimensional model of the hub motor into the finite element software, mesh the three-dimensional model of the hub motor, and set the analysis conditions, boundary conditions, material properties and solver of the harsh working conditions to form a finite element model;

[0009] By setting the brake pressure on the finite element model to perform stress analysis on the brake disc under severe working conditions, and setting the angular velocity to perform temperature analysis on the brake disc under severe working conditions, the stress analysis and temperature analysis results are coupled to determine the performance of the hub motor under high-temperature operating conditions.

[0010] Furthermore, the simplified processing includes equating the wheel movement during braking to pure rolling, the friction conforms to Coulomb's law, the braking pressure acting on the friction plate is a constant and uniformly distributed pressure, and the brake disc and the friction plate are both isotropic linear elastic materials.

[0011] Furthermore, the severe working condition includes an emergency braking condition, and setting the analysis conditions of the emergency braking condition includes: setting the initial speed of the vehicle, setting the time for the vehicle to decelerate to zero, and setting the solution time interval.

[0012] Furthermore, the severe working condition includes a continuous braking and dragging brake working condition, and setting the analysis conditions of the continuous braking and dragging brake working condition includes: setting to maintain the initial speed unchanged, setting the vehicle initial speed, setting the running slope, and setting the solution time interval.

[0013] Furthermore, the severe working conditions include continuous braking and long downhill drag braking conditions, and the analysis conditions for setting the continuous braking and long downhill drag braking conditions include: setting the initial speed to remain unchanged, setting the vehicle initial speed, setting the running slope, setting the continuous braking length of the long downhill, and setting the long downhill braking duration.

[0014] Furthermore, setting boundary conditions includes setting displacement boundary conditions and setting thermal boundary conditions. The displacement boundary conditions include constraining the translational freedom of the friction plate in the X and Y directions and constraining the translational freedom of the center point of the brake disc. The thermal boundary conditions include convection heat transfer coefficient and thermal radiation conditions.

[0015] Furthermore, setting the material properties includes setting the force contact properties and thermal contact properties of the friction pad and the brake disc.

[0016] Furthermore, the solver is an implicit solver.

[0017] A thermal coupling analysis system for wheel hub motors under harsh working conditions of disc brakes, including

[0018] A model building unit, used for simplifying the wheel hub motor model to form a simplified wheel hub motor three-dimensional model;

[0019] The finite element pre-processing unit imports the three-dimensional model of the hub motor into the finite element software, meshes the three-dimensional model of the hub motor, and sets the analysis conditions, boundary conditions, material properties and solvers of the harsh working conditions to form a finite element model;

[0020] Simulation analysis unit; used to perform stress analysis of the brake disc under severe working conditions by setting the brake pressure on the finite element model, and to perform temperature analysis of the brake disc under severe working conditions by setting the angular velocity, and to perform coupling analysis on the stress analysis and temperature analysis results to determine the performance of the hub motor under high-temperature operating conditions.

[0021] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method described above are implemented.

[0022] The beneficial effects of the present invention are:

[0023] The present invention establishes a three-dimensional model and imports it into finite element analysis software to perform mesh division, and sets information such as material parameters and boundary conditions to form a finite element model of the hub motor. The finite element model is then used to perform thermal coupling analysis of the hub motor. The performance and reliability of the integrated hub motor product in a braking high-temperature operating state can be simulated, and optimization directions can be found. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] like Figure 1 As shown, the present invention provides a hub motor thermal coupling analysis method based on disc brake under harsh working conditions. The key point is to analyze the maximum and occurrence time of the temperature field and stress field of the brake disc under the following three harsh working conditions, solve the temperature field of the motor and reducer at this time, and evaluate the risk, including the following steps:

[0027] Step 1, simplify the wheel hub motor model to form a simplified wheel hub motor three-dimensional model. The simplification is mainly for the treatment of the brake disc and the friction plate. The finite element method is used to analyze the temperature and stress changes of the brake during the braking process. It is assumed that during the braking process, the wheel only rolls, the friction conforms to Coulomb's law, and the braking pressure acting on the friction plate is constant and uniformly distributed; the friction plate is a composite material, and the brake disc and the friction plate are simplified to isotropic linear elastic materials. Their mechanical parameters and thermal parameters change with temperature. During the braking process, it is assumed that the initial temperature of the system is the same as the ambient temperature.

[0028] Step 2: Import the three-dimensional model of the hub motor into the finite element software, mesh the three-dimensional model of the hub motor, discretize it using hexahedron, set the analysis conditions, boundary conditions, material properties and solver of the harsh working conditions to form a finite element model.

[0029] The simulation analysis of three severe working conditions requires a lot of calculations. Based on the characteristics of the integrated hub motor, the analysis conditions of the severe working conditions are set, reasonable boundary conditions and material property input data are selected, and implicit calculation is used to improve the analysis efficiency. The mesh model is imported into the multi-physics field finite element analysis software, and the unit is selected as the C3D8RT thermal structure coupling unit. The thermal structure coupling finite element analysis of the disc brake is implemented using direct coupling and implicit solvers.

[0030] 2.1. Setting of analysis conditions for severe working conditions:

[0031] Condition 1: Emergency braking condition. The analysis conditions are: set the initial speed of the vehicle (before deceleration) (km / h), set the time to decelerate to zero (s), set the solution time interval (s). The solution time required to be set must take into account both the amount of calculation data and the ability to reflect key features.

[0032] Working condition 2: continuous braking and dragging brake working condition, the analysis conditions are: maintain the initial speed unchanged, set the vehicle initial speed (Km / h), set the running slope (%), set the solution time interval (s), the set solution time is required to take into account the calculation data volume and reflect the key characteristics, and the calculation is required to include the conversion of gravitational potential energy into heat energy generated by friction.

[0033] Condition 3: Continuous braking and long downhill dragging condition. The analysis conditions are: maintain the initial speed unchanged, set the vehicle initial speed (Km / h), set the running slope (%), set the continuous braking length of the long downhill slope (m), set the long downhill braking duration (min), set the solution time interval (s). The set solution time is required to take into account the amount of calculation data and reflect the key features. The calculation is required to include the conversion of gravitational potential energy into heat energy generated by friction.

[0034] 2.2. Setting of boundary conditions:

[0035] Setting boundary conditions includes setting displacement boundary conditions and setting thermal boundary conditions. The displacement boundary conditions are to constrain the translational freedom of the friction plate in the X and Y directions. In order to facilitate the application of angular velocity, a reference point is established at the center of the brake disc, and a rigid area is formed with the inner ring of the disc to constrain the translational freedom of the center of the brake disc. In the second analysis step, the angular velocity is applied, and the initial angular velocity applied in the emergency braking condition is set to (rad / s), and it is reduced to 0 within the braking time (s). Because the continuous braking condition is a "drag brake", the vehicle speed is maintained unchanged, so the angular velocity is maintained unchanged. In the analysis, the thermal boundary conditions need to apply the convective heat transfer coefficient and thermal radiation conditions, and the convective heat transfer coefficient of the friction plate (mW / mm 2 ℃). The convective heat transfer coefficient is calculated and linearized. This analysis considers surface radiation heat transfer, sets the emissivity eigenvalue to 0.6, sets absolute zero and Stefan-Boltzmann constant, and sets the initial temperature field to 20℃.

[0036] 2.3. Setting of material properties:

[0037] Thermal-structural coupling calculations require the establishment of contact-related properties between the friction pad and the brake disc, including force contact properties and thermal contact properties. Force contact uses the penalty function method, and the friction coefficient changes with temperature. Thermal contact requires setting the contact thermal conductivity (W / m.℃) of the contact interface. This data is generally determined by experimental methods. The contact thermal conductivity between the brake friction pairs is 10,000 to 30,000 W / m.℃. When the integrated hub motor brakes, the contact thermal conductivity can take a larger value through brake pressure control.

[0038] When the car brakes, emergency braking is the conversion of kinetic energy into friction heat, and continuous braking is the conversion of gravitational potential energy into friction heat. Assume that the friction heat conversion efficiency is 0.9. The heat generated by friction should be distributed to the brake disc and friction plate in a certain proportion. The heat flow distribution coefficient is derived from the one-dimensional heat conduction model as follows:

[0039]

[0040] Where γ is the heat flow distribution coefficient, k d is the thermal conductivity of the brake disc, c d is the specific heat of the brake disc, r d is the brake disc density; k p is the thermal conductivity of the friction plate, c p is the specific heat of the friction plate, r p is the friction plate density.

[0041] The heat flow ratio of the friction plate is:

[0042]

[0043] Where ζ is the heat flow ratio of the friction plate.

[0044] Step 3: The model uses finite element analysis to analyze the maximum and occurrence times of the temperature field and stress field of the brake disc under the following three severe working conditions, and then conducts a coupling analysis of the temperature field in combination with the temperature of the reducer and motor working conditions corresponding to the brake disc at each moment.

[0045] By setting the braking pressure on the finite element model, stress analysis of the brake disc under severe working conditions can be performed, and by setting the angular velocity, temperature analysis of the brake disc under severe working conditions can be performed. The performance of the hub motor under high-temperature braking operation can be determined by coupling analysis of the stress analysis and temperature analysis results.

[0046] The first analysis step is the static analysis load step, which is to perform stress analysis on the brake disc under severe working conditions by applying braking pressure to the finite element model, and obtain the stress field distribution diagram of the brake disc under three working conditions and the time when the maximum value occurs.

[0047] The second analysis step is the transient dynamic-temperature coupling load step, which is to perform temperature analysis of the brake disc under severe working conditions by applying angular velocity to the finite element model, and obtain the temperature field distribution diagram of the brake disc under three working conditions and the time when the maximum value occurs, and the angular velocity size.

[0048] The simulation analysis was carried out on the above three severe working conditions, and the maximum temperature and the maximum value of the first principal stress and the occurrence time table of each working condition were recorded respectively, as shown in Table 1 below. The stress was compared with the ultimate stress to confirm the reliability of the structure.

[0049] Table 1. Maximum values ​​and occurrence times of temperature and stress fields of brake discs under three working conditions

[0050]

[0051] Combined with the temperature of the reducer and motor operating conditions corresponding to the brake disc at each moment, a coupling analysis of the temperature field is performed, focusing on the main methods of heat conduction and heat convection. The heat radiation factor can be ignored in the analysis of this type of product.

[0052] After coupling analysis, simulation analysis is performed to obtain the temperature and maximum stress values ​​and distribution cloud diagrams of the integrated hub motor after different cumulative working times as shown in Table 2. Through analysis, it is possible to confirm whether the isolation measures between the motor, reducer and brake are effective and the optimization direction.

[0053] Table 2 Temperature and maximum stress value and distribution cloud diagram of integrated hub motor

[0054]

[0055]

[0056] In order to realize the above analysis method, the present invention also provides a hub motor thermal coupling analysis system based on the harsh working conditions of the disc brake, comprising:

[0057] A model building unit, used for simplifying the wheel hub motor model to form a simplified wheel hub motor three-dimensional model;

[0058] The finite element pre-processing unit is used to import the three-dimensional model of the hub motor into the finite element software, mesh the three-dimensional model of the hub motor, and set the analysis conditions, boundary conditions, material properties and solver of the harsh working conditions to form a finite element model;

[0059] Simulation analysis unit; used to perform stress analysis of the brake disc under severe working conditions by setting the brake pressure on the finite element model, and to perform temperature analysis of the brake disc under severe working conditions by setting the angular velocity, and to perform coupling analysis on the stress analysis and temperature analysis results to determine the performance of the hub motor under high-temperature operating conditions.

[0060] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the above-mentioned wheel hub motor thermal coupling analysis method and embodiment based on the harsh working conditions of the disc brake; or, when the computer program is executed by a processor, it implements the functions of each module / unit in the above-mentioned wheel hub motor thermal coupling analysis system based on the harsh working conditions of the disc brake.

[0061] Those skilled in the art may also understand that the various illustrative logical blocks, units, and steps listed in the embodiments of the present invention may be implemented by electronic hardware, computer software, or a combination of the two. In order to clearly demonstrate the interchangeability of hardware and software, the various illustrative components, units, and steps described above have generally described their functions. Whether such functions are implemented by hardware or software depends on the specific application and the design requirements of the entire system. Those skilled in the art may use various methods to implement the described functions for each specific application, but such implementation should not be understood as exceeding the scope of protection of the embodiments of the present invention.

[0062] The various illustrative logic blocks or units described in the embodiments of the present invention can be implemented or operated by a general-purpose processor, a digital signal processor, an application-specific integrated circuit (ASIC), a field programmable gate array or other programmable logic device, a discrete gate or transistor logic, a discrete hardware component, or any combination of the above. The general-purpose processor can be a microprocessor, and optionally, the general-purpose processor can also be any conventional processor, controller, microcontroller or state machine. The processor can also be implemented by a combination of computing devices, such as a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a digital signal processor core, or any other similar configuration.

[0063] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field.

Claims

1. A thermal coupling analysis method for wheel hub motors under harsh working conditions of disc brakes, characterized by: Simplifying the wheel hub motor model to form a simplified three-dimensional model of the wheel hub motor; Import the 3D model of the hub motor into the finite element software, perform meshing, and set the analysis conditions, boundary conditions, material properties and solver for harsh working conditions to form a finite element model; By setting the braking pressure on the finite element model, stress analysis of the brake disc under severe working conditions can be performed, and by setting the angular velocity, temperature analysis of the brake disc under severe working conditions can be performed. The performance of the hub motor under high-temperature operating conditions can be determined by coupling analysis of the stress analysis and temperature analysis results.

2. The thermal coupling analysis method of the wheel hub motor under the harsh working conditions of the disc brake according to claim 1 is characterized in that: The simplified processing includes equating the wheel movement during braking to pure rolling, the friction conforms to Coulomb's law, the braking pressure acting on the friction plate is constant and uniformly distributed, and the brake disc and the friction plate are both isotropic linear elastic materials.

3. The method for analyzing the thermal coupling of a hub motor under severe working conditions of a disc brake according to claim 1, characterized in that: The severe working condition includes an emergency braking condition, and setting the analysis conditions of the emergency braking condition includes: setting the initial speed of the vehicle, setting the time for the vehicle to decelerate to zero, and setting the solution time interval.

4. The method for analyzing the thermal coupling of a hub motor under severe working conditions of a disc brake according to claim 1 is characterized in that: The severe working condition includes continuous braking and dragging brake working condition, and setting the analysis conditions of the continuous braking and dragging brake working condition includes: setting to maintain the initial speed unchanged, setting the initial speed of the vehicle, setting the running slope, and setting the solution time interval.

5. The method for analyzing the thermal coupling of a hub motor under severe working conditions of a disc brake according to claim 1, characterized in that: The severe working conditions include continuous braking and long downhill drag braking conditions. The analysis conditions for setting the continuous braking and long downhill drag braking conditions include: setting the initial speed to remain unchanged, setting the vehicle initial speed, setting the running slope, setting the continuous braking length of the long downhill, and setting the long downhill braking duration.

6. The method for analyzing the thermal coupling of a hub motor under severe working conditions of a disc brake according to claim 1, characterized in that: Setting boundary conditions includes setting displacement boundary conditions and setting thermal boundary conditions. The displacement boundary conditions include constraining the translational freedom of the friction plate in the X and Y directions and constraining the translational freedom of the center point of the brake disc. The thermal boundary conditions include convection heat transfer coefficient and thermal radiation conditions.

7. The method for analyzing the thermal coupling of a hub motor under severe working conditions of a disc brake according to claim 1, characterized in that: Setting material properties includes setting the force contact properties and thermal contact properties of the friction pad and brake disc.

8. The method for analyzing the thermal coupling of a hub motor under severe working conditions of a disc brake according to claim 1, characterized in that: The solver is an implicit solver.

9. A thermal coupling analysis system for wheel hub motors under harsh working conditions of disc brakes, characterized by: include A model building unit, used for simplifying the wheel hub motor model to form a simplified wheel hub motor three-dimensional model; The finite element pre-processing unit is used to import the three-dimensional model of the hub motor into the finite element software to mesh the three-dimensional model of the hub motor, set the analysis conditions, boundary conditions, material properties and solver of the severe working conditions to form a finite element model; The simulation analysis unit is used to perform stress analysis of the brake disc under severe working conditions by setting the braking pressure on the finite element model, and to perform temperature analysis of the brake disc under severe working conditions by setting the angular velocity, and to perform coupling analysis on the stress analysis and temperature analysis results to determine the performance of the hub motor under high-temperature operating conditions.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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