Practical methods to control gear whine in transmission manufacturing process

<div class="section abstract"><div class="htmlview paragraph">Gear whine noise impacts customer perception of vehicle interior quietness in general and sound quality in particular. It has been a frequently occurred annoying phenomenon during vehicle development and much discussed topic regarding transmission NVH refinement in automotive industry. This work pertains to a transmission gear whine issue encountered in prototype evaluations during a vehicle program development process. The effort centers itself on the optimization of transmission gear macroscopic and microscopic parameters to fix the issue which is deemed unacceptable for customers. Specifically, by using multi-body dynamics approach, this work carries out a transmission system whine noise simulation based on optimal gear macro parameter selection and micro tooth flank modification. The obtained results show that the proposed design changes could successfully resolve the issue, which is verified by subsequent test measurement and confirmed by subjective evaluations. The work demonstrates that the containment of gear transmission error is an effective countermeasure to resolve the transmission gear whine noise issue.</div></div>

<div class="htmlview paragraph">Gear whine can be reduced through a combination of gear parameter selection and manufacturing process design directed at reducing the effective transmission error. The process of gear selection and profile modification design is greatly facilitated through the use of simulation tools to evaluate the details of the tooth contact analysis through the roll angle, including the effect of gear tooth, gear blank and shaft deflections under load. The simulation of transmission error for a range of gear designs under consideration was shown to provide a 3-5 dB range in transmission error. Use of these tools enables the designer to achieve these lower noise limits.</div> <div class="htmlview paragraph">An equally important concern is the dynamic mesh stiffness and transmissibility of force from the mesh to the bearings. Design parameters which affect these issues will determine the sensitivity of a transmission to a given level of transmission error. These dynamics are studied through the use of detailed finite element models of the transmission internals.</div> <div class="htmlview paragraph">A systematic approach to gear element design will be presented to optimize the gear blank design from the perspective of the influence both the transmission error and system dynamics on operating noise. The correlation of model predictions with measured operating data on prototype transmissions will be presented. The model results will be used to illustrate how the use of proper tuning of gear blank resonances can be used to further reduce noise levels by 5 - 10 dB.</div>

As vehicle overall noise levels are reducing, gear whine is becoming increasingly more of a nuisance. This paper illustrates a numerical method of predicting the Transmission Error (TE) at a gear mesh. It outlines a technique which applies an advanced genetic algorithm to optimise the gear tooth micro-geometry to minimise the Transmission Error (TE) and illustrates how the design can be made insensitive to manufacturing tolerances. A numerical simulation of the gearbox model is presented, which predicts the dynamic behaviour of a gearbox system, indicating modeshapes, frequencies and forces at the bearings. Finally, the numerical methods are verified by experimental techniques in a design case study, to reduce the gear whine of a vehicle transmission.

<div class="htmlview paragraph">The spur timing gears in Eaton superchargers operate at low torque loads and the supercharger system is especially sensitive to gear whine noise created by minute differences in the spur gear tooth profile quality. This has necessitated the grinding of very high quality profiles on high-contact-ratio spur gears. The manufacturing operation has used subjective evaluation of profile and lead measurements to qualify grinder diamonds and audit gear quality related to noise. They have also relied on supercharger end-of-line-testers to provide a direct measurement of gear noise as the primary quality feedback to the gear manufacturing process. Since the difference in the inspection plots of very high quality profiles is difficult to determine subjectively, the inspection process assessments have been difficult to correlate to the resultant gear noise measurements. The transmission error (TE) calculated from these profile measurements provided and objective assessment that was shown to correlate well with the actual measured gear whine noise. This study resulted in the creation of TE monitoring software that was an add-on to the inspection machine. This software, which uses a version of the LDP code (by The Ohio State Gear Dynamics Laboratory) as the core calculation routine, provides an objective metric of the gear mesh frequency TE and several harmonics calculated from the measured involute profile data. This objective TE metric provides a traceable standard for ensuring low vibration excitation in the gear mesh directly after grinding the gears.</div>

Unprecedented competition among the worldwide automotive manufacturers has benefited the consumer, resulting in higher levels of overall quality while simultaneously reducing the time-to-market for new models. One subjective differentiator of automotive quality is the noise and vibration performance, as evident by the quieter interiors even in vehicles not typically associated with the luxury banner, such a large trucks. In essence, passenger compartments devoid of objectionable road and wind noise have become a fundamental customer requirement expected in all vehicles regardless of cost, thereby reducing the broadband masking content of the interior. This reduction of masking has the potential to make tonal noise more prominent and annoying, by increasing the tone-to-noise ratio, and as result, the perception of quality may suffer. Gear whine is one such tonal noise phenomena that must be diligently managed by automotive engineers in order to avoid objectionable passenger compartment noise. This can be quite challenging, since many gear design features implemented for increased durability are often counter productive for noise. Sources of gear whine include powertrain components such as automatic and manuals transmissions, axles, transfer cases, power-take of units, engine accessory drives, and an assortment of other potential noise makers. This paper will attempt a technology review of various practical methods for managing the gear whine phenomena, including the use of Quality Function Deployment charts, dynamic transmission error with parametric gear models, and response surface modeling for gear design optimization.

<div class="section abstract"><div class="htmlview paragraph">Gear noise and vibration in automobile transmissions is a phenomenon of great concern. Noise generated at the gearbox, due to gear meshing, also known as gear whine, gets transferred from the engine cabin to the passenger cabin via various transfer paths and is perceived as air borne noise to the passengers in the vehicle. This noise due to its tonal nature can be very uncomfortable to the passengers. Optimizing micro-geometry of a gear pair can help in improving the stress distribution on tooth flank and reducing the sound level of the tonal noise generated during the running of the gearbox when that gear pair is engaged. This technical paper contains the study of variation in noise level in passenger cabin and contact on tooth flank with change in micro-geometry parameters (involute slope and lead slope) of a particular gear pair. Further scope of study has been discussed at the end of the paper.</div></div>

The modern theory of gearing is based on the design of gear drives according to the size and location of the contact pattern as well as the maximum level and type of the obtained function of transmission errors. These factors may reduce the life and the endurance of the gear drive for power transmission or even cause its failure. However, there is a factor that affects the quality perception of the performance of the gear drive and deserves to be taken into account in the design stage of the gear drive. It is called gear whine noise and it depends, among other factors, on the type and maximum level of the function of transmission errors. In this paper, an approach for the determination of the amplitude spectrum of different types and levels of functions of transmission errors is proposed in order to predict one of the sources of the radiated gear whine noise. The evaluation of the amplitude spectrum of the function of transmission errors will be made in terms of Fourier series, using the discrete Fourier transform. Therefore, the influence of the type and level of the function of transmission errors on the amplitude spectrum of their Fourier transforms will be investigated in order to find the suitable type of the function of transmission errors for reduction of the radiated gear whine noise and therefore for designing quiet gears.

This paper presents a new method to design a seventh-order transmission error for high contact ratio spiral bevel gears by the modified curvature motion method to reach the purpose of reducing or eliminating gear vibration and noise. In this paper, firstly, based on the predesigned seventh-order transmission error, the polynomial coefficients of transmission error curve can be obtained. Secondly, a method named modified curvature motion method is used to generate the spiral bevel gear with the predesigned transmission error. Lastly, based on TCA and LTCA, we verify the feasibility of the modified curvature motion method to generate spiral bevel gear with seventh-order transmission error, and the meshing impact of gear set with the seventh-order and second-order function of transmission error is analyzed and compared. The results of a numerical example show that the seventh-order transmission error acquired by the modified curvature motion method can effectively reduce the meshing impact of spiral bevel gears. The tooth modification method and meshing impact analysis method can serve as a basis for developing a general technique of flank modification for spiral bevel gears.

When designing helical gears, the goal is to optimize gear weight, efficiency, and noise while simultaneously achieving the required strength. In this study, the macro geometry of a helical gear pair was optimized for low weight, high efficiency, and low noise; further, trends of optimal solutions for five combinations of the three objectives were analyzed. The gear mass and efficiency were directly used as the design objectives. However, since the calculation of the gear noise is generally very complicated and time-consuming, the gear noise has not been directly used as the design objective, and the peak-to-peak static transmission error (PPSTE), which is the main source of the gear vibration, was selected as the design objective for the gear noise in the optimization. The objectives exhibited a trade-off relation between each other in the optimal space. If one of them was omitted, the objective considerably deteriorated. To analyze the results, the objectives were normalized and scored. As a result, most of the top ranks were from the optimal solutions considering the mass, efficiency, and PPSTE. Therefore, all three objectives should be considered in the gear optimization for low weight, high efficiency, and low noise.

This paper focuses on the gear whine noise problem of this engine, analyses it from two aspects of excitation source and transmission path, and puts forward the corresponding optimization method in combination with the actual product, which mainly includes the enhancement of the intrinsic frequency of the engine assembly, the optimization of the gear macro-parameters and the optimization of the gear micro-parameters. The optimization scheme achieves the objectives of minimizing transmission error and optimizing gear contact surface pressure and improves the NVH performance of the gear while considering the reliability of the gear system. Finally, the feasibility of the optimization scheme is verified by engine noise bench test. The study's results offer valuable insights for the design of diesel engine front-end gear systems, providing an effective approach to address existing product issues and to guide the development of new products.

Multi-objective and multi-step optimization of gear mesh is presented in this study which covers both macro and micro-geometry design variables. Two objective functions are considered including minimization of gear mesh power loss and transmission error (TE). Design constraints such as bending/contact stress limits, geometrical requirements and scuffing risk are introduced in optimization process. Scuffing is one of the most common surface failures in EV gear transmission due to high motor speed and output torque. Major causes include high contact pressure, high sliding velocity and surface temperature etc. The mainframe of its evaluation method applied in the analysis is based on AGMA standard which incorporates most tribological evaluation data needed. Some related key properties such as surface roughness and lubrication conditions are generated from more refined analysis or test results. For optimization method, a modified multi-objective particle swarm optimization (MOPSO) is applied which account for different aspects of gear performances and constraints. Results demonstrated significant reduction in both power loss and peak to peak TE at the end of iteration. Finally, the relationship among scuffing probability and other gear performance data are compared. It is indicated that optimized design with minimum power loss and TE does not have the lowest maximum surface temperature.

Traditionally, transmission error (TE) has been used in order to asses the noise properties of gears. Measurements of gear noise for a complete truck gearbox have been used to correlate noise from a gear pair with the concept of calculated static transmission error as noise excitation. Two gear pairs with very similar macro geometry but different micro geometry was used. Both transmission error as excitation and the excitation proposed by P. Velex and M. Ajmi which is the difference between the loaded and unloaded transmission error, are compared with measured noise. The result shows that the difference between the loaded and unloaded TE correlates well with measure noise for gear pair A but no excitation correlates with the measurement result gear pair B. A big difference between gear pair A and B can be seen in the contact pattern. The contact pattern of gear pair B shows that despite a large tip relief, edge contact occurs where the tip relief starts. This can be one explanation to the lack of correlation between TE and the measurement result for gear pair B. Another explanation can be other excitations such as friction and bending moments. The results show the limitations of only considering transmission error when designing quiet gears.

In every power transmission system, it is necessary to transmit the power effectively and smoothly. Any variations in transmission of power or torque will results in unwanted noise or vibrations development. Transmission Error (TE) is one of the factors which leads to noise or vibrations in gear transmission system. TE arises due to the various types of errors such as alignment error, tooth geometry error, backlash, cracks, profile error etc. in a gear pair. TE is the difference in the position of the output shaft from its actual position in a true gear pair. In this work the consequences occurring due to the change in number of teeth and pitch error on TE is observed using interference volume method. The spur gear pair of 1:1 gear ratio having involute tooth profile of standard and stub tooth proportions are taken for the work. The gears for the analyses are modelled and meshed/assembled in CAD software SOLIDWORKS. The interference volume values obtained during meshing are recorded for one mesh cycle of the gear pair. Then various graphs are plotted between the angle of rotation for one mesh cycle and interference volume values for different number of teeth and amount of pitch error. From the analyses it is found that the TE is affected when the number of teeth and amount of pitch error are varied. Also, the effects of variation of pitch error and number of teeth on TE is more in standard tooth proportion than stub tooth proportion.

This paper describes a new type planetary gear drive with the high reduction ratio. The planetary gear drive is mechanically similar to a 2S-C type planetary gear, which has two sun gears and one carrier. The planetary gear drive has two pairs of an arc tooth profile gear and a pin roller, which mesh each other. The planetary gear drive has little backlash, a high efficiency, a long fatigue limit, etc., because the tooth contact holds on concave and convex surfaces. In this study, we measured the vibration acceleration, the transmission error, the gear noise, and the efficiency on the new type planetary gear drive by the running test. We discuss and report the driving performance of the planetary gear drive.

Spur gears for many applications make use of profile shapes that are modifications of the mathematically defined involute to avoid premature tooth contact and unfavourable transmission error. It is well known that specification of the involute modification is important as it relates to the resulting performance, vibration and gear noise. In this research, a hybrid analysis method using finite elements and contact mechanics was used to investigate the effects of linear, parabolic and exponential tooth profile modifications on performance of an involute spur gear pair. For each type of modification, 10 different magnitudes of tip relief were used to study its influence on static transmission error (STE), tooth loads, root stresses and contact stresses. Peak-to-peak transmission error, root mean square transmission error and total area per cycle transmission error were used to characterise STE. Multiple output responses were calculated including the STE characteristics, tooth loads, tooth root stresses, contact stresses, gear moments and bearing forces to compare and contrast the type and magnitude of the tooth modification. Results show that linear modification produced low root stresses; parabolic modification produced low STE, contact stress, gear moment variations, and bearing force variations; exponential modification produced nearly the same STE characteristics over a wide range of tip modification magnitudes.