A design method of a transmission helical gear

Abstract

The application discloses a design method of a transmission helical gear, which comprises the following steps: S1, forming a plurality of groups of initial parameter combination data of the helical gear based on a product design task sheet; S2, taking coincidence degree as a constraint condition, calculating transmission errors of gear harmonics of each order, and evaluating whether the obtained transmission errors meet set requirements; S3, adopting a worm grinding wheel to grind the helical gear sample of the parameter combination of the helical gear preliminarily determined in S2, and microscopically measuring and evaluating whether the measured parameters meet design requirements; S4, identifying a wave amplitude and a wave number of regular textures of a tooth surface; and S5, under the constraint of the parameter combination of the helical gear preliminarily determined in S2, the wave amplitude and the wave number actually measured and read by S4 are brought in, transmission errors of gear harmonics of each order under the influence of the tooth profile wave of the ground gear are calculated, and whether the transmission errors meet set requirements is evaluated. The method can effectively reduce the risk of harmonic noise at the initial design stage, improve the NVH performance of the transmission, shorten the development cycle, and reduce the development cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile transmission, in particular to a design method of transmission helical gear. BACKGROUND

[0002] Gear whine is the main form of transmission noise, which is mainly caused by the unstable transmission in the process of gear meshing, and is a harmonic noise (similar to "whistling like" sine wave), the frequency of which is determined by the number of gear teeth and its speed. The masking effect of new energy vehicles is reduced, and the requirement for transmission noise is also improved. The gear process of transmission is also improved from shaving to grinding. The commonly used worm grinding process will cause regular texture on the surface of the gear, and then produce frequency whine, which is higher and more likely to cause customer complaints. On the engineering, the optimization measures of increasing the acceptance standard of parts or adding the acoustic package of the whole vehicle are usually used, the former reduces the qualified rate, and the latter increases the cost of the whole vehicle, so the economy of the optimization measures is not high.

[0003] Based on the current research, the transmission whine is caused by the transmission error of the tooth pair in the process of gear meshing, and the appropriate gear overlap is conducive to reducing the transmission error, so the current gear design is to improve the overlap as much as possible. In addition to the influence of the overlap, the gear surface texture also affects the gear frequency whine, and the control of the gear surface texture is currently in the control of the waviness in the gear processing stage.

[0004] CN105138734A discloses an improved helical gear noise optimization design method, which belongs to the field of optimization design of transmission gear. An improved Ishikawa method transmission helical gear main parameter optimization design method based on the theory of material mechanics is provided, which can reduce the transmission error of gear meshing, thereby reducing the vibration and noise in the meshing process, improving the service life and driving comfort. The method includes the following steps: step one, establishing a calculation model of the meshing dynamic stiffness and dynamic transmission error in the process of helical gear meshing, which is used to calculate the fluctuation value of the helical gear meshing dynamic transmission error; step two, based on the calculation model of step one and the gear design regulations, an optimization design model of the main parameters of the transmission helical gear is established, which aims to reduce noise and volume while ensuring strength and reliability in use, and the transmission helical gear is optimized; step three, the optimal parameters obtained by optimization design are tested to ensure the correctness of the optimization results. However, it still has the following problems: 1. The method does not take the gear overlap as a constraint condition, which is limited for gear whine noise optimization, and further does not form a design criterion based on reducing gear noise. 2. The relationship between gear frequency and gear parameters is not considered, so it is not possible to reasonably balance the design parameters of the fundamental frequency (meshing frequency) and the frequency. 3. The influence of gear processing surface texture parameters on high frequency (frequency) is not considered.

[0005] CN107194124A discloses a design method of a transmission helical gear, which comprises the following steps: establishing a transmission model by using Romax software, adjusting the structural parameters of the transmission within a certain range to arrange and combine gear pairs of each gear, screening the arranged and combined gear pairs according to constraint conditions, calculating the safety factor of the screened gear pairs and performing reliability screening, calculating the transmission error of the gear pairs screened by the reliability screening and performing comparative analysis. The design method can reasonably and accurately design the structural parameters of the transmission helical gear and reduce the howling noise of the transmission. However, it has the following problems: 1. Although the design standard of the contact ratio is given, the influence of the frequency multiplication and the application conditions are not considered. 2. The application in new energy reducers has limitations. The texture parameters of the ground gear have a great influence on the high-frequency noise of the gear. The application does not mention how to balance the texture parameters with the fundamental frequency parameters in the design stage.

[0006] The existing design of transmission helical gears usually uses contact ratio as a design constraint condition and uses transmission error as an evaluation standard of the gear howling performance in the design stage. However, the design standard of the contact ratio and the evaluation index of the transmission error given in the current literature are all based on the meshing fundamental frequency (meshing frequency), and the second-order harmonic and the third-order harmonic are not considered in the design stage, and the corresponding design standard of the contact ratio and the evaluation index of the transmission error are not formed.

[0007] The existing helical gear design of the transmission does not consider the influence of gear manufacturing related errors, usually product quality control is carried out in the manufacturing stage, and the management cost and time cost are also increased, and the consistency is difficult to guarantee. In fact, the gear errors generated by manufacturing contribute to the existence of each order harmonic of the gear. The second order harmonic is mainly caused by the tooth profile error, and the third order harmonic is mainly caused by the cutting error and the feed mark. With the improvement of gear machining process, the new energy reducer gear adopts the grinding process at present, and the grinding process precision can reach 5-6 levels, the pitch error, the tooth direction error and the surface roughness can be controlled in a small error range, for example: the tooth direction error can be stably controlled within ±5um in batch production (the grinding process generally requires ±7.5um). Therefore, for the new energy reducer product, the first order and fourth order harmonic risk caused by the tooth profile manufacturing error is low. Due to the influence of factors such as grinding efficiency, the worm grinding wheel is more used in the grinding process, which improves the precision of the gear, and also causes the tooth surface to form regular texture due to the grinding mechanism itself, wherein the tooth profile direction can be described by three parameters: wave amplitude, wave length and tooth surface wave direction. The wave amplitude and wave length have a greater impact on the second and third order harmonic noise. Changing the tool speed of the grinding machine can reduce the second and third order harmonic noise, but the noise reduction effect is not obvious. The stroke transmission model used for simulation and analysis has low precision, and the actual production has complex transmission curve, which makes it difficult to control the actual grinding machine, and also increases the equipment procurement and operation cost, so it is less used in actual engineering processing. SUMMARY

[0008] The purpose of the present application is to provide a design method of a transmission helical gear, which can effectively reduce the harmonic noise risk in the early design stage, improve the transmission NVH performance, shorten the development cycle and reduce the development cost.

[0009] The design method of the transmission helical gear provided by the present application comprises the following steps:

[0010] S1, forming a plurality of sets of helical gear initial parameter combination data based on the product design task book;

[0011] S2, taking the coincidence degree as the constraint condition, analyzing and calculating the transmission error of the first order gear harmonic, the second order gear harmonic and the third order gear harmonic of the plurality of sets of helical gear initial parameter combination data in S1, and evaluating whether the obtained transmission error meets the set requirement. If yes, the helical gear parameter combination is preliminarily determined, and S3 is entered; if not, S1 is returned;

[0012] S3, grinding the helical gear sample of the helical gear parameter combination preliminarily determined in S2 by using the worm grinding wheel, then performing microscopic measurement, and evaluating whether the measurement parameters meet the design requirements. If yes, S4 is entered; if not, regrinding is performed;

[0013] S4, identifying the amplitude and the number of regular textures of the tooth surface after grinding;

[0014] S5, under the constraint of the helical gear parameter combination preliminarily determined in S2, the amplitude and the number of regular textures read by S4 are brought in, the transmission error of the second-order gear harmonic and the third-order gear harmonic under the influence of the tooth profile corrugation of the ground gear is analyzed and calculated, and it is evaluated whether the obtained transmission error meets the set requirement. If yes, the helical gear parameter combination is taken as the design scheme. If no, the micro-shape modification parameters of the tooth profile are adjusted, and S2 to S5 are repeated.

[0015] Further, S6 is further included. Under the constraint of the helical gear parameter combination determined in S5, the number of regular textures with the highest frequency in S4 is brought in, the transmission error of different amplitudes of the regular textures is checked and analyzed, and the amplitude control standard of the regular textures is determined.

[0016] Further, S1 is specifically: according to the transmission center distance provided by the design task, the speed ratio of each gear pair, and the set helix angle, pressure angle, normal modulus, tooth number, tooth width, modification coefficient, backlash, tooth profile chamfer, tooth tip chamfer, and machining allowance of each helical gear, a transmission model is established by using Romax software, and the coincidence degree data of each gear pair is obtained from the transmission model,

[0017] By using Romax software, the helix angle and / or the pressure angle and / or the tooth width and / or the normal modulus and / or the speed ratio of each gear pair of the transmission model is adjusted within the adjustment range of the helix angle and / or the pressure angle and / or the tooth width and / or the normal modulus and / or the speed ratio of each gear pair of each helical gear, and a plurality of sets of gear pair combinations and corresponding coincidence degree data are obtained and saved, that is, a plurality of sets of initial parameter combination data of the helical gear are formed.

[0018] Further, S2 is specifically: according to the coincidence degree constraint condition, the plurality of sets of initial parameter combination data of the helical gear formed in S1 are screened by using Romax software, the initial parameter combination of the helical gear meeting the coincidence degree constraint condition is screened by the constraint condition, the finite element method solver in Romax software is used for solving, and the transmission error of all the initial parameter combinations of the helical gear screened by the constraint condition is calculated.

[0019] Further, the measurement parameters in S3 include error, tooth shape error, tooth profile error, tooth profile tilt error, tooth drum amount, tooth profile drum amount, pitch cumulative error, and tooth ring radial runout error.

[0020] Further, the transmission error setting requirement of each order gear harmonic in S2 is specifically: when helical gears are used in MT transmission or DCT transmission, the transmission error amplitude of the first order gear harmonic is ≤1.0 μm, and the transmission error amplitudes of the second order gear harmonic and the third order gear harmonic are both ≤0.5 μm;

[0021] When helical gears are used in hybrid transmission, the transmission error amplitude of the first order gear harmonic is ≤0.8 μm, and the transmission error amplitudes of the second order gear harmonic and the third order gear harmonic are both ≤0.3 μm.

[0022] Further, S4 is specifically: the three-dimensional atlas of the regular texture of the tooth surface after gear grinding is simplified into a plurality of two-dimensional tooth profile corrugation curves which are sequentially stacked along the tooth width direction, and the corrugation amplitude and the number of waveforms of the regular texture of the tooth surface after gear grinding are identified by evaluating different two-dimensional tooth profile corrugation curves and the tooth profile three-section curves of the same tooth.

[0023] Compared with the prior art, the present application has the following beneficial effects.

[0024] 1. In the early design stage, the present application takes coincidence degree as a constraint condition, analyzes and calculates a plurality of sets of initial parameter combination data of helical gears to obtain the transmission error of the first order gear harmonic, the second order gear harmonic and the third order gear harmonic, thereby effectively reducing the risk of harmonic noise in the early design stage, improving the helical gear harmonic noise, improving the transmission NVH performance, especially significantly reducing the noise of new energy reducer, effectively reducing customer complaints, reducing the redesign of gear scheme caused by frequency multiplication harmonic noise, shortening the development cycle, reducing the development cost, avoiding the design of gear grinding equipment cutter variable speed processing in the later stage, and reducing the processing cost and cycle of parts.

[0025] 2. The present application takes coincidence degree as a constraint condition, and combines the specific limitation of the transmission error setting requirement of each order gear harmonic, so that the gear noise generated by the second order and third order harmonics can be effectively reduced, and the later scheme optimization and rectification caused by insufficient consideration of harmonic influence in the design of helical gear parameters can be avoided, thereby saving development costs.

[0026] 3. The present application uses tooth profile shape error and tooth profile waveform number to represent the tooth surface fluctuation amplitude and wavelength of tooth profile topography respectively, identifies the two-dimensional tooth surface topography parameters, and uses common gear measuring equipment to measure the corresponding data. At the same time, the tooth profile shape error and the waveform number are used to evaluate the tooth profile topography feature points corresponding to the maximum corrugation amplitude, so that all fluctuation points are avoided to be analyzed and evaluated, and the subsequent CAE analysis is simplified.

[0027] 4, The worm grinding wheel is used for grinding the helical gear sample with the preliminarily determined parameter combination of the helical gear, then micro measurement is carried out, and whether the measurement parameters meet the design requirements is evaluated, then the corrugation amplitude and the wave number read by the actual measurement are brought into the preliminarily determined parameter combination of the helical gear, the transmission error of the second order gear harmonic and the third order gear harmonic under the influence of the ground gear profile corrugation is analyzed and calculated, whether the obtained transmission error meets the set requirements is evaluated, the manufacturing error is introduced into the helical gear design, the secondary correction of the micro modification parameters of the helical gear is carried out, the frequency multiplication noise problem caused by the inherent process manufacturing error is avoided, and the product performance stability is improved. This method can also avoid the problems of equipment modification cost increase and variable speed control precision error caused by the variable speed processing technology.

[0028] 5, Under the constraint of the determined parameter combination of the helical gear, the wave number with the highest occurrence frequency is brought in, the transmission error of different corrugation amplitudes under the wave number is analyzed, the corrugation amplitude control standard is determined, the quality control of mass production products can be more accurately realized, and the product consistency is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a flow chart of the design method of the transmission helical gear according to the present application;

[0030] Figure 2 is a three-dimensional map of the regular texture of the tooth surface after grinding;

[0031] Figure 3 is a two-dimensional tooth profile corrugation curve schematic diagram;

[0032] Figure 4 is a definition schematic diagram of the wave number;

[0033] Figure 5 is an actual measurement curve schematic diagram in the embodiment of the present application;

[0034] Figure 6 is a transmission error curve diagram of each corrugation amplitude under 1 wave;

[0035] Figure 7 is a transmission error curve diagram of each corrugation amplitude under 1.5 waves. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0037] Referring to Figure 1 , the design method of the transmission helical gear is shown, which comprises the following steps:

[0038] S1, based on the product design task book, form several sets of helical gear initial parameter combination data, specifically: according to the transmission center distance, the speed ratio of each gear pair and the set helical gear helix angle, pressure angle, normal modulus, tooth number, tooth width, modification coefficient, backlash, tooth profile chamfer, tooth crest chamfer, machining allowance provided by the design task book, the Romax software is used to establish the transmission model, and the coincidence degree data of each gear pair is obtained from the transmission model.

[0039] Using Romax software, adjusting the helix angle and / or pressure angle and / or tooth width and / or normal modulus and / or speed ratio of each gear pair of each helical gear in the adjustment range of the helix angle and / or pressure angle and / or tooth width and / or normal modulus and / or speed ratio of each gear pair of the transmission model, obtaining and saving several sets of gear pair combinations and corresponding coincidence degree data, that is, forming several sets of helical gear initial parameter combination data.

[0040] S2, using Romax software, according to the coincidence degree constraint condition, screening the several sets of helical gear initial parameter combination data formed by S1, the helical gear initial parameter combination meeting the coincidence degree constraint condition is screened by the constraint condition, and the FE solver in Romax software is used to solve the finite element method, and the transmission error of all helical gear initial parameter combinations screened by the constraint condition is calculated. Evaluate whether the obtained transmission error meets the set requirement, if yes, preliminarily determine the helical gear parameter combination, enter S3, if not, return to S1.

[0041] Among them, the coincidence degree constraint condition of each order gear harmonic is shown in Table 1, and the transmission error set requirement of each order gear harmonic is shown in Table 2.

[0042] Table 1 Coincidence degree constraint condition of each order gear harmonic

[0043]

[0044] Table 2

[0045]

[0046] S3, using worm grinding wheel to grind the helical gear sample of the helical gear parameter combination preliminarily determined by S2, and then performing microscopic measurement, the purpose of which is to read the tooth surface ripple characteristics generated by the inherent grinding characteristics of the equipment under stable processing. In the measurement, in order to facilitate the identification of ripple details, the measurement scale needs to meet ≥1000:1. The measurement parameters include error f Hβ, the tooth trace shape error f fβ , the tooth profile shape error f fα , the tooth profile tilt error f Hα , the tooth trace drum amount C β , the tooth profile drum amount C α , the pitch cumulative error F p , the gear ring radial runout error F r .

[0047] The microscopic measurement mainly includes the following two steps: ① randomly selecting any three teeth on the gear circumference for microscopic measurement, in order to avoid adjacent teeth, and to measure the three teeth as far as possible equidistantly along the gear circumference; ② randomly selecting one tooth from the three teeth that have been measured microscopically, and respectively measuring the tooth trace and the tooth profile direction of the tooth profile three sections, wherein the tooth profile three sections refer to that the tooth profile curve of the helical gear draws three parallel lines from the tooth top to the tooth root along the tooth profile direction, and the tooth profile measurement results on the three lines are the tooth profile three sections.

[0048] It is judged whether the measurement parameters meet the design requirements, if yes, S4 is entered, if not, the gear grinding is re-performed, and specifically, the error f Hβ , the tooth trace shape error f fβ , the tooth profile shape error f fα , the tooth profile tilt error f Hα , the tooth trace drum amount C β , the tooth profile drum amount C α , the pitch cumulative error F p , the gear ring radial runout error F r meet the process requirements, for example, the tooth profile shape error f fα ≤7.5um, the tooth profile drum amount C α≤ 5.0um, which are determined according to the self-standard of each host factory, and the consistency needs to meet the standard requirement of ≤11, wherein the consistency includes the different tooth consistency and the same tooth consistency, for example, the measurement values of the tooth trace shape error f fβ of the tooth trace three sections of the same tooth are-5um, 6um and 8um respectively, and the same tooth consistency is 8um-(-5um) = 13um, which does not meet the requirement. If the evaluation measurement parameters meet the design requirements, the finished parts meet the drawing requirements, that is, the actual parameters of the parts do not deviate from the design, S4 is entered. If not, the gear grinding is re-performed, the microscopic measurement is performed, and the evaluation is performed again according to the above standard.

[0049] In S4, the wave amplitude and the number of waveforms of the regular texture of the tooth surface after gear grinding are identified; since the regular texture caused by the worm grinding wheel gear grinding process mainly affects the tooth profile direction, we only need to identify and analyze the texture characteristics in the tooth profile direction. Referring to Figure 2Because the regular texture of the ground tooth surface is distributed in three-dimensional space and the distribution is complex, we only observe the tooth profile direction. (See [reference]). Figure 3 The three-dimensional map is simplified into multiple two-dimensional tooth profile ripple curves superimposed along the tooth width direction. The three parameters characterizing the tooth surface texture in the two-dimensional tooth profile ripple curve are: the amplitude f of the tooth surface ripple. wa The wavelength λ of tooth surface ripple a The direction of tooth surface undulation L a Each two-dimensional tooth profile corrugation curve represents the measurement result along the tooth profile direction in S3. Simultaneously, we can roughly assess the consistency of the tooth profile corrugation along the tooth profile direction by referring to the data from the three cross-sections of the tooth profile. Therefore, by evaluating different two-dimensional tooth profile corrugation curves and the three cross-section curves of the same tooth profile, key tooth profile texture features can be identified. Among the measurement parameters, the tooth profile shape error f... fα The industry definition is: the distance between two curves that perfectly enclose the actual tooth profile and are identical to the average tooth profile. In engineering practice, only the impact of the maximum ripple on harmonic noise is of concern. Therefore, combining the definition of ripple amplitude, the largest tooth shape error f among the various tooth profile measurement curves can be selected. fα As the maximum approximation of the ripple amplitude, i.e., the maximum risk value of the process error, it is used for subsequent simulation verification. Gear harmonics are related not only to the ripple amplitude but also to the number of corresponding waveform cycles. This invention uses the number of waveforms to characterize the cycle situation corresponding to the ripple amplitude; see [link to relevant documentation]. Figure 4 We define half a sine wave as a 0.5 waveform, one sine wave as a 1.0 waveform, and so on. See also... Figure 6 According to the above definition, waveforms are read on the actual measurement curve. Waveforms with amplitudes greater than 2µm mainly include 1 and 1.5 waveforms. Since a larger period corresponds to lower harmonic excitation, and the perception of low frequencies is generally weaker with higher tolerance, analysis is usually performed on cases with 2 or fewer waveforms.

[0050] S5. Under the constraints of the helical gear parameter combination initially determined in S2, the ripple amplitude and waveform number actually measured and read in S4 are input, and the transmission error of the second-order gear harmonic and the third-order gear harmonic under the influence of the ground tooth profile ripple is analyzed and calculated. The transmission error is evaluated to see if it meets the set requirements. If it does, the helical gear parameter combination is used as the design scheme. If not, the tooth profile micro-modification parameters are adjusted, and S2 to S5 are repeated.

[0051] S6, under the constraint of the helical gear parameter combination determined in S5, substitute the number of waveforms that appear most frequently in S4, and perform transmission error verification analysis on different ripple amplitudes under this number of waveforms to determine the ripple amplitude control standard and achieve precise control of key NVH indicators of products in the mass production stage.

[0052] According to the designed helical gear parameter combination, entity sample is made, bench test and whole vehicle test are completed, and before the product is put on the market, the design and control parameters are checked through whole vehicle small batch verification feedback and failure case, and reasonable review and revision are provided for data accumulation and guidance for subsequent product development.

[0053] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of designing a variable transmission helical gear, characterized by, Comprise the following steps: S1, based on product design task book forms several groups of helical gear initial parameter combination data; S2, with coincidence degree as constraint condition, analyzes and calculates the transmission error of first order gear harmonic, second order gear harmonic and third order gear harmonic of several groups of helical gear initial parameter combination data in S1, evaluates whether the obtained transmission error meets the set requirement, if yes, preliminarily determines the helical gear parameter combination, enters S3, if not, returns to S1; S3, adopts worm grinding wheel to grind the helical gear preliminarily determined in S2, then carries out micro measurement, and evaluates whether the measured parameters meet the design requirement, if yes, enters S4, if not, regrinds the helical gear; S4, identifies the wave amplitude and wave number of regular texture of the tooth surface after grinding; S5, under the constraint of the helical gear parameter combination preliminarily determined in S2, the wave amplitude and wave number read by S4 are brought in, the transmission error of second order gear harmonic and third order gear harmonic under the influence of gear shape wave is analyzed and calculated, whether the obtained transmission error meets the set requirement is evaluated, if yes, the helical gear parameter combination is taken as the design scheme, if not, the micro modification parameters of gear shape are adjusted, and S2 to S5 are repeated.

2. The design method of a helical gear of a transmission according to claim 1, characterized in that: Further comprising S6, under the constraint of the helical gear parameter combination determined in S5, the wave number with the highest occurrence frequency in S4 is brought in, the different wave amplitudes under the wave number are checked and analyzed to determine the wave amplitude control standard.

3. The design method of a transmission helical gear according to claim 1 or 2, characterized in that, S1 is specifically: according to the transmission center distance, the speed ratio of each gear pair and the set helix angle, pressure angle, normal modulus, tooth number, tooth width, displacement coefficient, backlash, tooth profile chamfer, tooth tip chamfer and machining allowance of each helical gear provided by the design task book, a transmission model is established by using Romax software, the coincidence degree data of each gear pair is obtained from the transmission model, By using Romax software, the helix angle and / or pressure angle and / or tooth width and / or normal modulus and / or speed ratio of each gear pair of the transmission model is adjusted within the adjustment range of the helix angle and / or pressure angle and / or tooth width and / or normal modulus and / or speed ratio of each gear pair, a plurality of gear pair combinations and corresponding coincidence degree data are obtained and saved, that is, a plurality of groups of helical gear initial parameter combination data are formed.

4. The design method of a transmission helical gear according to claim 1 or 2, characterized in that, S2 is specifically: according to the coincidence degree constraint condition, the plurality of groups of helical gear initial parameter combination data formed in S1 are screened by using Romax software, the helical gear initial parameter combination meeting the coincidence degree constraint condition passes the constraint condition screening, the finite element method solver in Romax software is used for solving to calculate the transmission error of all the helical gear initial parameter combinations passing the constraint condition screening.

5. The design method of a helical gear of a transmission according to claim 1 or 2, characterized in that: The measured parameters in S3 include error, tooth shape error, tooth profile error, tooth profile tilt error, tooth drum amount, tooth drum amount, pitch cumulative error and tooth ring radial runout error.

6. The design method of a transmission helical gear according to claim 1 or 2, characterized in that, The setting requirement of the transmission error of each order gear harmonic in S2 is specifically: when the helical gear is used in the MT transmission or the DCT transmission, the amplitude of the transmission error of the first order gear harmonic is ≤1.0 μm, and the amplitudes of the transmission errors of the second order gear harmonic and the third order gear harmonic are both ≤0.5 μm; When the helical gear is used in the hybrid transmission, the amplitude of the transmission error of the first order gear harmonic is ≤0.8 μm, and the amplitudes of the transmission errors of the second order gear harmonic and the third order gear harmonic are both ≤0.3 μm.

7. The design method of a transmission helical gear according to claim 1 or 2, characterized in that, S4 is specifically: the three-dimensional atlas of the regular texture of the tooth surface after gear grinding is simplified into a plurality of two-dimensional tooth profile corrugation curves which are sequentially stacked along the tooth width direction, and the corrugation amplitude and the wave number of the regular texture of the tooth surface after gear grinding are identified by evaluating different two-dimensional tooth profile corrugation curves and the tooth profile three-section curves of the same tooth.

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