Gear Noise Reduction through Transmission Error Control and Gear Blank Dynamic Tuning

<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>

<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">The production unit number of small diesel engine cars tends to decline except recreational vehicles in Japanese market in recent years, while the production unit number in Europe market keeps on increasing owing to the merits of the durability and the fuel consumption. The small diesel engines will have to be improved in the near future by solving major problems such as noise and vibration pollution, environmental pollution, improvement in performance of diesel engines, in order to expand the production of the engines.</div> <div class="htmlview paragraph">This paper refers to a basic study on the experimental and analytical methods for the reduction of resonant vibration in each vibration mode on some cylinder blocks of small high-speed diesel engines in rated engine speed range. Hammering test method, which is easy and useful for measuring frequency response functions, is carried out in the experiments. In this test, the cylinder blocks are directly excited with the impulse hammer, and more the main journals are excited via the newly-made force transmission parts in the next experiment. Two kinds of the engines which have been recently recognized as low noise and vibration engines are chosen in this study. The cylinder blocks of the engines are called of long skirt type and ladder frame type, respectively. The vibration characteristics of these cylinder blocks are obtained in the frequency range from 500 <i>Hz</i> to 2 <i>kHz</i> using the experimental modal analysis. This frequency range is chosen in consideration of the reliability of the vibration experiments. And the force transmission routes from the piston heads to the crank journals of each cylinder block are considered as mentioned in the latter experimental method. The experimental results are used to calculate the natural frequencies by the modal analysis and the calculated results are compared with the ones obtained from FEM analysis. Furthermore, the cylinder blocks are remodeled in order to reduce the vibrations of all modes using FEM analysis.</div> <div class="htmlview paragraph">Consequently, it has been shown that the vibration stress of the cylinder block can be reduced by higher rigidities and more lightening weights of the crankcase and the crank journals in the measured frequency range.</div> <div class="htmlview paragraph">The conclusions are described as follows;</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts is useful to measure the natural frequencies of a cylinder block. This method can be easy to get the equal results with the measured ones on running conditions without engine operation.</div> </li> <li class="list-item"> <span class="li-label">2</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts can easily analyze the natural frequencies at all the vibration modes on equal conditions with running ones. Then the method is a useful tool for improving the vibration characteristics.</div> </li> <li class="list-item"> <span class="li-label">3</span> <div class="htmlview paragraph">It has been proved from the analytical viewpoints that the cylinder block of the ladder frame type can be adopted as low-noise, small diesel engines with little increase of the engine weight while maintaining higher rigidity.</div> </li> </ol> </div>

<div class="section abstract"><div class="htmlview paragraph">The use of simulation tools by vehicle manufacturers to design, optimize and validate their vehicles is essential if they are to respond to the demands of their customers, to meet legislative requirements and deliver new vehicles ever more quickly. The use of such tools in the aerodynamics community is already widespread, but they remain some way from replacing physical testing completely. Further advances in simulation capabilities depend on the availability of high quality validation data so that simulation code developers can ensure that they are capturing the physics of the problems in all the important areas of the flow-field.</div><div class="htmlview paragraph">This paper reports on an experimental program to generate such high quality validation data for a SAE 20 degree backlight angle notchback reference model. This geometry is selected as a particularly powerful test case for the development and validation of numerical tools because the flow exhibits a realistic impingement and A pillar regime, significant three dimensional structures and the backlight/boot-deck exhibits a local separation and reattachment. The paper includes force and moment data, surface pressures for the centerline, slant, boot-deck and base and detailed PIV data for the impingement region, model centerline, A pillar and multiple planes on the slant and boot-deck. Time averaged, statistical and instantaneous data are presented.</div><div class="htmlview paragraph">Results are discussed with regard to the overall flow features, the correlation between the different data sets and the accuracy and limitations of each of the experimental techniques in this particular application. Example data is included throughout the paper and full data sets are freely available in the Loughborough University Institutional Repository as a resource for future code development.</div></div>

<div class="section abstract"><div class="htmlview paragraph">IN this paper the author explains a new method for the determination of the fatigue life of bevel and hypoid gears. This method is said to offer a means for comparing various tooth forms and gear mountings.</div><div class="htmlview paragraph">Briefly, it consists of making a layout in the mean normal section of the tooth, and of calculating the tensile stress in the fillet when the maximum load is applied at its highest position on the tooth. Consideration is given to the fact that in cases where the contact ratio is sufficient to ensure at least two teeth in contact at all times the load will be divided between the teeth. Such factors as impact, inertia, and temperature are given consideration.</div><div class="htmlview paragraph">A graph is plotted using this calculated stress and the number of cycles to failure resulting from extensive bending fatigue tests on both bevel and hypoid gears. With the aid of this graph the fatigue life of new gear designs may be estimated.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Within gear pair development, the simulation of loaded transmission error, line of action and summarized mesh point are crucial information in design optimization as well as reliability, NVH and efficiency prediction. These properties and variables are difficult to evaluate and are usually only assessed through proxy-variables such as unloaded transmission error or contact pattern assessment. Alternatively, large design loops can be generated when prototypes are produced to directly assess the results of reliability, NVH and efficiency and simulation models updated to the results, but not directly calibrated.</div><div class="htmlview paragraph">This work will showcase an advanced test facility with the unique capabilities to evaluate all gear contact types (including hypoid, beveloid, cylindrical and spiral) under loaded conditions while assessing position and force data that can be used to validate simulation models directly and enhance design development.</div><div class="htmlview paragraph">Results will be shown for the assessment of hypoid gear fatigue life while also showing the effect of manufacturing tolerances on performance and the evolution of these critical variables throughout the life as they vary with run-in and gradual flank wear.</div></div>

Gear whine of automotive transmissions should be controlled since it is of a nuisance. While many methods are used to control gear whine at gear design stage, this paper deals with it in transmission manufacturing process including gear manufacturing and transmission assemblies. There are high percentages of effects on transmission error and gear whine in these two processes. Idle gear whine noise can be reduced by the introduction of hard finishing which can optimize the gear shapes and surfaces. Bending of helical gear is found playing an important role in generating high frequency gear whine. It is significant for transmission assemblies to study the correlations of End of Line (EOL) and vehicles. The satisfying correlations can identify and control gear whine of an assembled transmission. All the methods mentioned above have been applied in transmission manufacturing process and good results have been achieved.

The Internet and World Wide Web (WWW) are now evolving as an important communication technology and a major information resource provider for industry. This paper discusses the development and implementation of a knowledge-based gear design and manufacturing system over the Internet to create new integrated design and manufacturing environments. By providing access to an interactive web-based support system, any designer with a WWW browser becomes a potential user of this on-line design system. Once connected, the designer follows the system instructions and submits the necessary input data on the appropriate web pages. The server receives a request from a client and invokes a CGI (Common Gateway Interface) program that processes the information provided through the user Interface. The CGI parses the data and has the ability to remotely run the knowledge-based gear design system that integrates knowledge about all aspects of gear design and manufacturing and provides powerful reasoning and decision-making capabilities for reducing the time between gear tooth creation, detailed design and manufacturing process specification via the Internet. When the execution is completed, full specifications definition, geometry, kinematic-loads and stresses are determined through Finite Element Analysis (FEA) within ANSYS, VRML models of the gear pair and gearbox assembly including gears, shafts, bearings and housing are exported according to the designer requests and sent back to designer on the web browser. To accomplish this, a combination of HTML, JavaScript, VRML, CGI Script and C++ is used. Finally, an example on spur gear design utilizing a parallel gearbox design model configuration is discussed.

<div class="htmlview paragraph">The frequent use of large transport aircraft on soft and rough airfields in or near battle zones requires that they be fitted with landing gears having increased capability for ground flotation and shock absorption.</div> <div class="htmlview paragraph">Design and parametric studies of aircraft landing gears show feasible approaches to the problems associated with soft and rough airfields. Landing gear concepts, analytical methods, and design parameters are presented for airplanes of 110,000–750,000 lb gross weight.</div> <div class="htmlview paragraph">Landing gear weights, sizes, and configurations are compared, and their soft and rough field capabilities are evaluated.</div> <div class="htmlview paragraph">Structural and dynamic aspects of rough field operations are discussed for bare soil fields and for fields covered with landing mats.</div>

<div class="section abstract"><div class="htmlview paragraph">An open-link locomotion module (OLLM) is an autonomous energy self-sufficient locomotion setup for designing ground wheeled vehicles of a given configuration that includes drive/driven and steered/non-steered wheels with individual suspension and brake systems. Off-road applications include both trucks and trailers. The paper concentrates on the module's electro-hydraulic suspension design and presents results of analytical and experimental studies of a trailer with four driven (no wheel torque applied) open-link locomotion modules.</div><div class="htmlview paragraph">On highly non-even terrain, the suspension design provides the sprung mass with sufficient vibration protection at low level of normal oscillations, enhanced damping and stabilized angular movements. This is achieved by the introduction of two control loops: (i) a fast-acting loop to control the damping of the normal displacements; and (ii) a slow-acting control loop for varying the pressure and counter-pressure in the suspension system. Thus, two separate but coordinated controls were designed for both loops to act under small (less than ±7 degrees) and big (larger than ±7 degrees) pitch and roll angles of a vehicle designed with a set of the modules.</div><div class="htmlview paragraph">The control actions in both loops of each module are distributed among the trailer's modules through three control channels: one channel to damp normal oscillations of each module and another two channels to stabilize the pitch and roll angles. This paper presents details on the loop controls and the channels and shows the ride efficiency of the suspension system in the 0.5-10 Hz frequency range of the sprung mass vibrations; some details on potential break-down (bottoming) of the suspension prototype are provided based on experimental study of a newly designed trailer with four open-link locomotion modules. Many other suspension design problems (including suspension bandwidth, power requirements, <i>etc.</i>) are not in the scope of the paper.</div></div>

<div class="htmlview paragraph">Due to protection applicances in the car, fewer persons sustain injuries in the course of traffic accidents. It can be pointed out that the injury pattern of car occupants was visibly changed by the seat belt, in earlier years the windscreen and steering wheel could hardly still be regarded as injury sources, but in the current situation with belt using of over 90% the injuries of all injured car drivers occur under other circumstances:</div> <div class="htmlview paragraph">19% of all injured car drivers suffered injuries by the steering wheel, 20% by the dashboard, 29% by belt load and 14% caused by parts of the footroom region.</div> <div class="htmlview paragraph">It can be summarized that the present car safety measures did not avoid all major injuries and lower limb injuries occur relatively often.</div> <div class="htmlview paragraph">This study will explain the injury mechanisms of lower limb injuries and show demands for car developments and dummy test work. The data has been derived from traffic accidents documented by scientific team at the Accident Research Unit of the Medical University Hannover / Germany, by order of the Federal Highway Research Institute BAST.</div> <div class="htmlview paragraph">Out of a sample of 6985 belted drivers in car crashes 2,605 belted car drivers with lower limb injuries could be analysed. Persons with pelvic fractures as well as isolated hip joint fractures were included. The accidents are documented during the years 1985 to 94 within a statistical random sample and weighting procedure.</div> <div class="htmlview paragraph">In the study it was established that the injury risk for the legs is different in various collision types as frontal and lateral impact. Impacts of the vehicle side against a tree cause the most frequent and the most severe consequences. The different kinds and localisations of injuries are shown related to accident severity parameter like Delta-v and the influence of intrusion will be analysed. The pelvis has to be included in the explanation of mechanisms. Important for the resulting injury are impulse direction and position of lateral force transmission.</div> <div class="htmlview paragraph">Isolated femural fractures are incured when a direct impact to the thigh region occurs distinctly in front of the pelvis laterally or transversally. A combination of femural and pelvic fractures can be found when the impact occurs transversally from the front. Isolated pelvic fractures are found when the lateral impact involves the pelvic region. Pelvic girdle fractures do also often determine a transverse longitudinal axis component. Pelvic fractures were exposed to high collision severity. They occur mainly in lateral impacts, especially with poles.</div> <div class="htmlview paragraph">The kind of interior deformation is responsible for the kind of injury pattern and the intrusion can be seen as an important influence factor.</div>

<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>

<div class="section abstract"><div class="htmlview paragraph">Electric vehicles offer cleaner transportation with lower emissions, thus their increased popularity. Although, electric powertrains contribute to quieter vehicles, the shift from internal combustion engines to electric powertrains presents new Noise, Vibration, and Harshness challenges. Unlike traditional engines, electric powertrains produce distinctive tonal noise, notably from motor whistles and gear whine. These tonal components have frequency content, sometimes above 10 kHz. Furthermore, the housing of the powertrain is the interface between the excitation from the driveline via the bearings and the radiated noise (NVH). Acoustic features of the radiated noise can be predicted by utilising the transmitted forces from the bearings. Due to tonal components at higher frequencies and dense modal content, full flexible multibody dynamics simulations are computationally expensive. Based on previously developed metrics for sound quality, a methodology is proposed with the requirements to design a reduced order model, coupling analytical solutions for the electrical motor along with lumped parameter powertrain modelling. Namely, for an adequate representation of the tonal content, the proposed model considers the harmonic excitations of the electric motor and torque ripple, time-varying stiffness and backlash for the meshing gears and flexibility of the housing at the bearing connection points. The reduced order model predicts the transmitted bearing forces, enabling an overview of the sound quality of the radiated noise with lower computational time and complexity.</div></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="htmlview paragraph">An investigation of transmission errors and bearing contact of spur, helical and spiral bevel gears was performed. Modified tooth surfaces for these gears have been proposed in order to absorb linear transmission errors caused by gear misalignment and localize the bearing contact. Numerical examples for spur, helical, and spiral bevel gears are presented to illustrate the behavior of the modified gear surfaces to misalignment and errors of assembly. The numerical results indicate that the modified surfaces will perform with a low level of transmission error in non-ideal operating environment.</div>