A new energy vehicle composite transmission reducer and its reliable durability verification method

Abstract

The present invention discloses a durability verification method for a composite transmission reducer of a new energy vehicle, comprising the following steps: Step 1, obtaining a gear pair in the composite transmission reducer, wherein the gear pair comprises a driven gear made of 20CrMnTi and an active gear made of PEEK material; Step 2, according to the parameters of each pair of gear pairs, the Maugis-Dugdale contact theory is used to calculate the contact stress, thereby performing strength verification; Step 3, after meeting the strength verification requirements, according to the three-parallel-axis two-stage gear transmission configuration, it is integrated into a set of composite transmission reducers, and the integrated reducer is reliably and durablely verified. This method solves the problem that the prior art method is not suitable for reliable and durable design verification of steel / polymer gear composite transmission devices.

Description

Technical Field

[0001] The present invention relates to the technical field of power transmission for new energy vehicles, and in particular to a composite transmission reducer for new energy vehicles and a durability verification method thereof. Background Art

[0002] As a combination of components that transmit power and motion, the gear system plays an important role in the transmission device of new energy vehicles. In recent years, with the research and development of high-performance engineering polymers and the continuous upgrading of precision injection molding technology, the load-bearing power of polymer gears has been continuously improved, reaching more than 30kW, achieving a breakthrough from simple motion transmission to power transmission, and has been successfully applied to new energy vehicle reducers and other fields, and has continued to evolve towards high power and large size, which has effectively promoted the transformation trend of "plastics replacing steel" in the gear industry.

[0003] Polymer gears are used in the transmission system of new energy vehicles, which helps to reduce the mass and rotational inertia of the system, improve power density and control accuracy, increase the overlap and load balance of gear pairs, and thus promote energy conservation and emission reduction, optimize vibration and noise, and improve multiple performances of the vehicle. However, since polymer gears are significantly weaker than steel gears in terms of strength, stiffness, thermal conductivity and wear resistance, the use of steel / polymer gear composite transmission solutions can fully combine the high strength, high hardness, and wear resistance of steel with the lightweight, self-lubricating, and corrosion-resistant characteristics of polymer materials, which helps to give full play to their respective advantages and develop new composite transmission devices.

[0004] The current reliable and durable design verification methods for gear transmission devices are usually divided into the following steps:

[0005] The first step is to comprehensively design the transmission route of the transmission device and clarify the transmission device configuration based on the design input of the new energy vehicle, such as the vehicle's dynamic and economic indicators, hybrid or pure electric drive function, the maximum output torque, power, and speed of the power source, the number of gears and speed ratio range, the operating environment and lubrication conditions, etc.

[0006] The second step is to select the processing material of the gear. For steel gears, 20CrMo, 20CrMnTi, 20MnCr5 and other steel types are usually selected.

[0007] The third step is to design the macro and micro parameters of each pair of gear pairs, including center distance, number of teeth, module, pressure angle, helix angle, displacement coefficient, tooth profile crown, tooth inclination, etc.

[0008] The fourth step is to perform strength check according to the design parameters of each pair of gear pairs, mainly contact fatigue strength check and bending fatigue strength check. Usually, the contact fatigue strength check uses the Hertz stress as the basis for calculating the contact stress of the tooth surface to evaluate the contact strength; the bending fatigue strength check uses the maximum tensile stress at the root of the tooth profile as the nominal bending stress, which is corrected by the corresponding coefficient as the calculated bending stress. The calculated contact stress and calculated bending stress are respectively less than the allowable contact stress and allowable bending stress of the material and have a certain safety factor, which means that the strength check requirements are met.

[0009] The fifth step is to integrate each pair of gear pairs that meet the strength verification into a composite transmission device according to the transmission device configuration determined in the first step, and conduct reliability and durability verification on the integrated transmission device. By setting the operating conditions and cycle times of the transmission device, verify whether the transmission device has gear failure and determine whether it meets the reliability and durability performance requirements.

[0010] The above steps are often aimed at transmission devices composed entirely of steel gears. However, for composite transmission devices composed of steel / polymer gears, due to differences in material composition, contact mechanism, mechanical model, dynamic meshing characteristics, durability and reliability verification methods, etc., there are significant differences in the selection of processing materials in the second step, the strength verification of gear pairs in the fourth step, and the reliable durability verification of transmission devices in the fifth step for steel / polymer composite transmission devices. The existing technical methods are no longer applicable. Summary of the invention

[0011] In view of the deficiencies in the prior art, the present invention proposes a composite transmission reducer for new energy vehicles and a durability verification method thereof. The method is aimed at a composite transmission device composed of steel / polymer gears, and innovations are made in gear material selection, gear strength verification, reliable durability verification, etc. The method adopts theoretical models and analysis methods such as polymer material performance analysis, steel / polymer gear pair contact mechanism analysis, polymer material nonlinear mechanical model, steel / polymer gear viscoelastic coupling dynamic model, time-temperature effect analysis, etc., to solve the problem that the prior art methods are not suitable for reliable durability design verification of steel / polymer gear composite transmission devices.

[0012] In order to solve the above technical problems, the technical solution of the present invention is:

[0013] A composite transmission reducer for new energy vehicles comprises a plurality of gear pairs, each pair of the gear pairs comprises a driving gear and a driven gear, the driving gear is made of polymer material, and the driven gear is made of steel material.

[0014] Preferably, the polymer material is any one of POM, PA, and PEEK, and the steel material is any one of 20CrMo, 20CrMnTi, and 20MnCr5.

[0015] Preferably, the transmission route of the compound transmission reducer adopts a three-parallel-shaft two-stage gear transmission configuration of an input shaft, an intermediate shaft, and an output shaft.

[0016] Preferably, the parameters of the gear pair meet the standards for application of transmission reducers in new energy vehicles.

[0017] Preferably, the parameters include center distance, number of teeth, module, helix angle, pressure angle, displacement coefficient, tooth profile crown, and tooth inclination.

[0018] A durability verification method for a new energy vehicle composite transmission reducer comprises the following steps:

[0019] Step 1, obtaining a gear pair in a composite transmission reducer, wherein the gear pair comprises a driven gear made of 20CrMnTi and a driving gear made of PEEK material;

[0020] Step 2: According to the parameters of each pair of gear pairs, the Maugis-Dugdale contact theory is used to calculate the contact stress, so as to perform strength verification;

[0021] Step 3: After meeting the strength verification requirements, integrate them into a set of composite transmission reducers according to the three-parallel-axis two-stage gear transmission configuration, and conduct reliability and durability verification on the integrated reducer.

[0022] Preferably, the mathematical expression of the Maugis-Dugdale contact theory model is as follows:

[0023]

[0024]

[0025]

[0026] in, The net contact force is the vector sum of the forces between two objects when they are in contact; is the elastic contact force; is the viscous contact force; is the elastic modulus; is the effective contact radius; and are the action radius of elastic contact force and the action radius of viscous contact force respectively; is the stress factor and is a constant.

[0027] Preferably, the maximum contact stress between the driving gear and the driven gear is calculated as follows:

[0028]

[0029]

[0030] in, is the maximum contact stress of the driven gear, is the maximum contact stress of the driving gear.

[0031] Preferably, in step 2, during the strength check, the maximum contact stress of the driven gear and the maximum contact stress of the driving gear are respectively less than the allowable contact stress of the corresponding materials and have a safety factor, that is, the strength check requirement is met.

[0032] Preferably, the operating environment of the composite transmission reducer is set according to the vehicle dynamics index of the new energy vehicle, and the operating conditions and cycle times of the reducer are set with reference to the standards, and then a durability test is carried out.

[0033] Preferably, the durability test of the composite transmission reducer is conducted based on the time-temperature equivalence principle and is conducted within the temperature range of the time-temperature equivalence principle.

[0034] The present invention has the following characteristics and beneficial effects:

[0035] The above technical solutions are adopted to improve the design accuracy and applicability. Through the reasonable selection of steel gear materials (such as 20CrMo, 20CrMnTi, 20MnCr5) and polymer gear materials (such as POM, PA, PEEK), and the evaluation of the different properties of particle-reinforced, fiber-reinforced and hybrid-reinforced polymers, higher strength, stiffness, fatigue resistance, better toughness and wear resistance are achieved, thereby improving the design accuracy and applicability.

[0036] Improvements in strength verification. The introduction of Maugis-Dugdale contact theory and Kelvin-Voigt constitutive model can more accurately describe the nonlinear behavior of steel / polymer gear pairs during contact and bending. These models can more accurately predict contact and bending stresses and better evaluate the contact and bending strength of polymer gears, thereby improving the safety and reliability of the design.

[0037] Improved efficiency of reliable and durable verification. By using the time-temperature equivalence principle, reliable and durable verification can be completed in a shorter time, which greatly shortens the verification cycle and improves the design and development efficiency, which is crucial to speeding up the research and development of new energy vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0039] Figure 1 The figure is a flow chart of a method according to an embodiment of the present invention.

[0040] Figure 2 It is a time-temperature equivalent principle diagram in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0042] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings.

[0043] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. Those skilled in the art can fully understand the present invention without the description of these details.

[0044] Example 1

[0045] The present embodiment provides a composite transmission reducer for new energy vehicles, including a plurality of gear pairs, each pair of the gear pairs including a driving gear and a driven gear, the driving gear is made of polymer material, and the driven gear is made of steel material. Among them, the driven gear is usually made of steel types such as 20CrMo, 20CrMnTi, 20MnCr5, etc.; the driving gear can usually be made of different types of polymers such as POM, PA, PEEK, etc. according to different design inputs. Each polymer material can be divided into particle-reinforced polymers, fiber-reinforced polymers, and mixed-reinforced polymers due to different fillers. Particle-reinforced polymers usually have better toughness and wear resistance, while fiber-reinforced polymers usually have higher strength, stiffness and fatigue resistance. Mixed-reinforced polymers achieve better comprehensive performance by optimizing the ratio and distribution of the two. Therefore, when selecting polymer gear materials, due to the diversity of polymer types and polymer filling components, there are large differences in the mechanical properties of different polymer gears, and corresponding choices need to be made according to the design input.

[0046] In this embodiment, the driving gear is made of PEEK material, and the driven gear is made of 20CrMnTi. The driving gear is made of PEEK material reinforced with silica particles and carbon fiber, which takes into account toughness, wear resistance, strength, rigidity, and fatigue resistance, and achieves better comprehensive performance.

[0047] Furthermore, the transmission route of the compound transmission reducer adopts a three-parallel-shaft two-stage gear transmission configuration of an input shaft, an intermediate shaft, and an output shaft.

[0048] Specifically, in this embodiment, according to the design input of the pure electric vehicle, the vehicle's dynamic indicators are a maximum speed of 80 km / h, a maximum climbing grade of 20%, an acceleration time of 0-80 km / h of 12 seconds, and an economic indicator of electricity consumption of 13 kWh per 100 kilometers. The maximum output torque of the drive motor is 100 Nm, the power is 50 kW, the speed is 8000 rpm, the fixed speed ratio is 10.3, splash lubrication and other conditions. The transmission route of the transmission device is comprehensively designed, and a two-stage gear transmission configuration with three parallel shafts, an input shaft, an intermediate shaft, and an output shaft is adopted.

[0049] Among them, the macroscopic parameters and microscopic parameters of the gear pair in the compound transmission reducer meet the standards of the compound transmission reducer for new energy vehicles. Specifically, the macroscopic parameters and microscopic parameters include center distance, number of teeth z, module , pressure angle α, helix angle β, displacement coefficient, tooth profile crown, and tooth inclination.

[0050] Example 2

[0051] This embodiment provides a durability verification method for a new energy vehicle composite transmission reducer. Figure 1 As shown, the following steps are included:

[0052] Step 1: Get the gear pair in the composite transmission reducer. In this embodiment, for the composite transmission reducer composed of steel / polymer, the steel gear is made of 20CrMnTi; the polymer gear is made of PEEK material reinforced by silica particles and carbon fiber, taking into account toughness, wear resistance, strength, stiffness, and fatigue resistance to achieve better comprehensive performance. Among them, the driving gear is made of PEEK material, and the driven gear is made of steel material.

[0053] Step 2: According to the parameters of each pair of gear pairs, the Maugis-Dugdale contact theory is used to calculate the contact stress and thus perform strength verification.

[0054] It is understandable that since the calculation method in the "Calculation Method of Load Capacity of Involute Cylindrical Gears" (GB / T 3480-1997) is based on the Hertz contact theory, it is no longer applicable to the calculation of tooth surface contact stress of steel / PEEK gear pairs. The Maugis-Dugdale contact theory is required to calculate the contact stress and evaluate the contact strength.

[0055] Specifically, the Maugis-Dugdale contact theory model is a viscoelastic contact model that takes into account the energy loss and local deformation characteristics in the actual contact process. The mathematical expression of this model is:

[0056] (1)

[0057] in, The net contact force is the vector sum of the forces between two objects when they are in contact; is the elastic contact force; is the viscous contact force.

[0058] Furthermore, the elastic contact force

[0059] (2)

[0060] Viscous contact force

[0061] (3)

[0062] in, is the elastic modulus; is the effective contact radius; and are the action radius of elastic contact force and the action radius of viscous contact force respectively; is the stress factor and is a constant.

[0063] Further, solve , substitute the relevant parameters of the gear pair.

[0064] Specifically, formula (1) It can be expressed as:

[0065] (4)

[0066] In the formula, is the gear pair load torque, is the gear pair module, is the number of teeth in the gear pair.

[0067] In formula (2), and , , Related, respectively expressed as:

[0068] (5)

[0069] (6)

[0070] (7)

[0071] In formula (5), and are the elastic modulus of steel and PEEK respectively; and are the Poisson's ratios of steel and PEEK respectively. In formula (7), and are the radii of the contact points of the steel and PEEK gear pitch circles. Taking steel gears as an example, It can be further expressed as:

[0072] (8)

[0073] Combining equations (5) to (8), we can solve .

[0074] In formula (3), and , Related, respectively expressed as:

[0075] (9)

[0076] (10)

[0077] Among them, in formula (9), is the width of the viscous zone. In formula (10), is the fracture energy of the material, which describes the material's ability to resist crack propagation. Combining equations (6), (9), and (10), we can solve .

[0078] Furthermore, according to the macroscopic contact force , , , respectively solve the maximum contact stress of steel and PEEK gears, which can be expressed as:

[0079] (11)

[0080] (12)

[0081] Step 3: Integrate each pair of steel / PEEK gear pairs that meet the strength verification into a set of composite transmission reducers according to the three-parallel-axis two-stage gear transmission configuration specified in the first step, and verify the reliability and durability of the integrated reducer. Set the operating conditions and cycle times of the reducer with reference to national standards, industry standards or enterprise standards, verify whether the reducer has gear failure, and determine whether it meets the reliability and durability performance requirements.

[0082] In this embodiment, each pair of gear pairs that meet the strength verification is integrated into a set of composite transmission reducers according to the three-parallel-axis two-stage gear transmission configuration, and the integrated reducer is verified for reliability and durability. With reference to national standards, industry standards, and enterprise standards, the operating conditions and cycle times of the reducer are set to verify whether the reducer has gear failure and whether it meets the reliability and durability performance requirements. The composite transmission reducer can be based on the time-temperature equivalence principle, such as Figure 2 As shown, the expression is as follows:

[0083] (13)

[0084] in, is the mobile factor, it can be seen that when ;when In this embodiment, the temperature is within the time-temperature equivalence principle temperature range (143°C ~340°C).

[0085] It should be noted that the scope of application of the time-temperature equivalence principle is mainly in the temperature range above the glass transition temperature (Tg) and below the melting temperature (Tm) of polymer materials. The operating temperature of the lubricating oil of the pure electric vehicle reducer is generally -40 °C~130 °C. The tooth surface temperature of polymer gears is relatively high due to friction and low thermal conductivity. PEEK material has stable mechanical properties at -70 °C ~ 250 °C, its Tg is about 143 °C, and its Tm is about 340 °C. Due to friction and low thermal conductivity, the tooth surface temperature of PEEK gears will be higher than the ambient temperature. According to the time-temperature equivalence principle, appropriately increasing the test temperature of the steel / PEEK reducer to 120°C can speed up the durability reliability test verification and shorten the test time.

[0086] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments including components are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A durability verification method for a composite transmission reducer of a new energy vehicle, characterized in that: The steps include: Step 1, obtaining a gear pair in a composite transmission reducer, wherein the gear pair comprises a driven gear made of 20CrMnTi and a driving gear made of PEEK material; Step 2: According to the parameters of each pair of gear pairs, the Maugis-Dugdale contact theory is used to calculate the contact stress, so as to perform strength verification; The Maugis-Dugdale contact theory model is a viscoelastic contact model, which takes into account the energy loss and local deformation characteristics in the actual contact process. The mathematical expression of the model is: P=P1+P a (1) Where P is the net contact force, which refers to the vector sum of the forces between two objects when they are in contact; P1 is the elastic contact force; P a is the viscous contact force; The elastic contact force P1 can be expressed as: The viscous contact force P a It can be expressed as: Among them, E * is the elastic modulus; R is the effective contact radius; a e and a v are the elastic contact force action radius and the viscous contact force action radius respectively; σ0 is the stress factor, which is a constant; Solve for P, P1, P a , substitute the relevant parameters of the gear pair; Formula (1) P can be expressed as: Where, T is the gear pair load torque, m n is the gear pair module, z is the number of gear pair teeth; P1 and E in formula (2) * 、a e , R, respectively expressed as: In formula (5), E1 and E2 are the elastic moduli of steel and PEEK respectively; v1 and v2 are the Poisson's ratios of steel and PEEK respectively; in formula (7), R1 and R2 are the radii of the contact points of the pitch circles of steel and PEEK gears respectively; taking steel gears as an example, R1 can be further expressed as: Combining equations (5) to (8), we can solve P1; P in formula (3) a with a e 、a v Related, respectively expressed as: In formula (9), δ is the width of the viscous zone, and in formula (10), G c is the fracture energy of the material, which describes the material's ability to resist crack propagation. Combining equations (6), (9), and (10), we can solve P a ; According to the macro contact forces P, P1, P a , respectively solve the maximum contact stress of steel and PEEK gears, which can be expressed as: Step 3: After meeting the strength verification requirements, integrate them into a set of composite transmission reducers according to the three-parallel-axis two-stage gear transmission configuration, and conduct reliability and durability verification on the integrated reducers. The durability test of the composite transmission reducer is based on the time-temperature equivalence principle and is carried out within the temperature range of the time-temperature equivalence principle. The composite transmission reducer is based on the time-temperature equivalence principle, and the expression is as follows: E(T1,t1)=E(T2,t2)=E(T2,t1a T ) (13) Among them, a T is the shift factor. It can be seen that when T1 > T2, a T > 1; when T1 < T2, a T < 1. Within the temperature range of 143°C to 340°C of the time-temperature equivalence principle, according to the time-temperature equivalence principle, the test temperature of the steel / PEEK reducer is increased to 120°C.

2. The durability verification method of a new energy vehicle composite transmission reducer according to claim 1 is characterized in that: In step 2, during the strength check, the maximum contact stress of the driven gear and the maximum contact stress of the driving gear are respectively less than the allowable contact stress of the corresponding materials and have a safety factor, that is, the strength check requirements are met.

3. The durability verification method of a composite transmission reducer for a new energy vehicle according to claim 2 is characterized in that: The operating environment of the composite transmission reducer is set according to the vehicle dynamics index of the new energy vehicle, and the operating conditions and cycle times of the reducer are set with reference to the standards, and then a durability test is carried out.

4. The durability verification method of a composite transmission reducer for a new energy vehicle according to claim 3 is characterized in that: The transmission route of the new energy vehicle composite transmission reducer adopts a three-parallel-shaft two-stage gear transmission configuration of an input shaft, an intermediate shaft, and an output shaft.

5. The durability verification method of a composite transmission reducer for a new energy vehicle according to claim 4 is characterized in that: The parameters of the gear pair meet the standards for the application of transmission reducers in new energy vehicles.

6. The durability verification method of a composite transmission reducer for a new energy vehicle according to claim 5 is characterized in that: The parameters include center distance, number of teeth, module, helix angle, pressure angle, displacement coefficient, tooth profile crown, and tooth inclination.

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