【正文】 on briefly describes the activities involved in reducing gear noise from a wheel loader aim is to show how the optimization of the gear geometry described in Paper E is used in an industrial author was project manager for the “noise work team” and performed the gear of the requirements when developing a new automatic power transmission for a wheel loader was improving the transmission gear existing power transmission was known to be driving at high speed in fourth gear, a high frequency gearwhine could be there were now demands for improved sound transmission is a typical wheel loader power transmission, consisting of a torque converter, a gearbox with four forward speeds and four reverse speeds, and a dropbox partly integrated with the dropbox is a chain of four gears transferring the powerto the output gears are engaged by wet multidisc clutches actuated by the transmission hydraulic and control Gear noise target for the new transmission Experience has shown that the high frequency gear noise should be at least 15 dB below other noise sources such as the engine in order not to be perceived as disturbing or showed that if the gear noise could be decreased by 10 dB, this criterion should be satisfied with some analysis of the noise measured in the driver39。s cab showed that the dominant noise from the transmission originated from the dropbox goal for transmission noise was thus formulated as follows: “The gear noise(sound pressure level)from the dropboxgears in the transmission should be decreased by 10 dB pared to the existing transmission in order not to be perceived as was assumed that it would be necessary to make changes to both the gears and the transmission housing in order to decrease the gear noise sound pressure level by 10 Noise and vibration measurements In order to establish a reference for the new transmission, noise and vibration were measured for the existing transmission is driven by the same type of diesel engine used in a wheel engine and transmission are attached to the stand using the same rubber mounts that are used in a wheel loader in order to make the installation as similar as possible to the installation in a wheel output shaft is braked using an electrical Optimization of gears Noiseoptimized dropbox gears were designed by choosing macroand microgeometries giving lower transmission error than the original(reference) gear geometry was chosen to yield a low transmission error for the relevant torque range, while also taking into consideration variations in the microgeometry due to manufacturing optimization of one gear pair is described in more detail in Paper error is considered an important excitation mechanism for gear [1] defines it as “the difference between the actual position of the output gear and the position it would occupy if the gear drive were perfectly conjugate.” In this project the aim was to reduce the maximum predicted transmission error amplitude at gear mesh frequency(first harmonic of gear mesh frequency)to less than 50% of the value for the reference gear first harmonic of transmission error is the amplitude of the part of the total transmission error that varies with a frequency equal to the gear mesh torque range of 100 to 500 Nm was chosen because this is the torque interval in which the gear pair generates noise in its design to Welbourn [1], a 50% reduction in transmission error can be expected to reduce gearbox noise by 6 dB(sound pressure level, SPL).Transmission error was calculated using the LDP software(Load Distribution Program)developed at the Gear Laboratory at Ohio State University [3].The “optimization” was not strictly design was optimized by calculating the transmission error for different geometries, and then choosing a geometry that seemed to be a good promise, considering not only the transmission error, but also factors such asstrength, losses, weight, cost, axial forces on bearings, and choosing microgeometric modifications and tolerances, it is important to take manufacturing options and cost into goal was to use the same finishing method for the optimized gears as for the reference gears, namely grinding using a KAPP VAS 531 and CBNcoated grinding a specific torque and gear macrogeometry, it is possible to define a gear microgeometry that minimizes transmission example, at no load, if there are no pitch errors and no other geometrical deviations, the shape of the gear teeth should be true involute, without modifications like tip relief or involute a specific torque, the geometry of the gear should be designed in such a way that it pensates for the differences in deflection related to stiffness variations in the gear , even if it is possible to define the optimal gear microgeometry, it may not be possible to manufacture it, given the limitations of gear must also be given to how to specify the gear geometry in drawings and how to measure the gear in an inspection many applications there is also a torque range over which the transmission error should be that manufacturing tolerances are inevitable, and that a demand for smaller tolerances leads to higher manufacturing costs, it is important that gears be other words, the important characteristics, in this case transmission error, must not vary much when the torque is varied or when the microgeometry of the gear teeth varies due to manufacturing [3] was used to calculate the transmission error for the reference and optimized gear pair at different torque robustness function in LDP was used to analyze the sensitivity to deviations due to manufacturing “min, max, level” method involves assigning three levels to each Optimization of transmission housing Finite element analysis was used to optimize the transmission optimization was not performed in a strictly mathematical way, but was done by calculating the vibration of the housing for different geometries and then choosing a geometry that seemed to be a good was not the sole consider