1、机械专业论文中英文对照Gearbox NoiseCorrelation with Transmission Error and Influence of Bearing PreloadABSTRACTThe five appended papers all deal with gearbox noise and vibration. The first paper presents a review of previously published literature on gearbox noise and vibration.The second paper describes a tes
2、t rig that was specially designed and built for noise testing of gears. Finite element analysis was used to predict the dynamic properties of the test rig, and experimental modal analysis of the gearbox housing was used to verify the theoretical predictions of natural frequencies.In the third paper,
3、 the influence of gear finishing method and gear deviations on gearbox noise is investigated in what is primarily an experimental study. Eleven test gear pairs were manufactured using three different finishing methods. Transmission error, which is considered to be an important excitation mechanism f
4、or gear noise, was measured as well as predicted. The test rig was used to measure gearbox noise and vibration for the different test gear pairs. The measured noise and vibration levels were compared with the predicted and measured transmission error. Most of the experimental results can be interpre
5、ted in terms of measured and predicted transmission error. However, it does not seem possible to identify one single parameter,such as measured peak-to-peak transmission error, that can be directly related to measured noise and vibration. The measurements also show that disassembly and reassembly of
6、 the gearbox with the same gear pair can change the levels of measured noise and vibration considerably.This finding indicates that other factors besides the gears affect gear noise.In the fourth paper, the influence of bearing endplay or preload on gearbox noise and vibration is investigated. Vibra
7、tion measurements were carried out at torque levels of 140 Nm and 400Nm, with 0.15 mm and 0 mm bearing endplay, and with 0.15 mm bearing preload. The results show that the bearing endplay and preload influence the gearbox vibrations. With preloaded bearings, the vibrations increase at speeds over 20
8、00 rpm and decrease at speeds below 2000 rpm, compared with bearings with endplay. Finite element simulations show the same tendencies as the measurements.The fifth paper describes how gearbox noise is reduced by optimizing the gear geometry for decreased transmission error. Robustness with respect
9、to gear deviations and varying torque is considered in order to find a gear geometry giving low noise in an appropriate torque range despite deviations from the nominal geometry due to manufacturing tolerances. Static and dynamic transmission error, noise, and housing vibrations were measured. The c
10、orrelation between dynamic transmission error, housing vibrations and noise was investigated in speed sweeps from 500 to 2500 rpm at constant torque. No correlation was found between dynamic transmission error and noise. Static loaded transmission error seems to be correlated with the ability of the
11、 gear pair to excite vibration in the gearbox dynamic system.Keywords: gear, gearbox, noise, vibration, transmission error, bearing preload.ACKNOWLEDGEMENTSThis work was carried out at Volvo Construction Equipment in Eskilstuna and at the Department of Machine Design at the Royal Institute of Techno
12、logy (KTH) in Stockholm. The work was initiated by Professor Jack Samuelsson (Volvo and KTH), Professor Sren Andersson (KTH), and Dr. Lars Brthe (Volvo).The financial support of the Swedish Foundation for Strategic Research and the Swedish Agency for Innovation Systems VINNOVA is gratefully acknowle
13、dged. Volvo Construction Equipment is acknowledged for giving me the opportunity to devote time to this work.Professor Sren Andersson is gratefully acknowledged for excellent guidance and encouragement.I also wish to express my appreciation to my colleagues at the Department of Machine Design, and e
14、specially to Dr. Ulf Sellgren for performing simulations and contributing to the writing of Paper D, and Dr. Stefan Bjrklund for performing surface finish measurements.The contributions to Paper C by Dr. Mikael Prssinen are highly appreciated. All contributionsto this work by colleagues at Volvo are
15、 gratefully appreciated.1 INTRODUCTION1.1 BackgroundNoise is increasingly considered an environmental issue. This belief is reflected in demands for lower noise levels in many areas of society, including the working environment. Employees spend a lot of time in this environment and noise can lead no
16、t only to hearing impairment but also to decreased ability to concentrate, resulting in decreased productivity and an increased risk of accidents. Quality, too, has become increasingly important. The quality of a product can be defined as its ability to fulfill customers demands. These demands often
17、 change over time, and the best competitors in the market will set the standard.Noise concerns are also expressed in relation to construction machinery such as wheel loaders and articulated haulers. The gearbox is sometimes the dominant source of noise in these machines.Even if the gear noise is not
18、 the loudest source, its pure high frequency tone is easily distinguished from other noise sources and is often perceived as unpleasant. The noise creates an impression of poor quality. In order not to be heard, gear noise must be at least 15 dB lower than other noise sources, such as engine noise.1
19、.2 Gear noiseThis dissertation deals with the kind of gearbox noise that is generated by gears under load.This noise is often referred to as “gear whine” and consists mainly of pure tones at high frequencies corresponding to the gear mesh frequency and multiples thereof, which are known as harmonics
20、. A tone with the same frequency as the gear mesh frequency is designated the gear mesh harmonic, a tone with a frequency twice the gear mesh frequency is designated the second harmonic, and so on. The term “gear mesh harmonics” refers to all multiples of the gear mesh frequency.Transmission error (
21、TE) is considered an important excitation mechanism for gear whine. Welbourn 1 defines transmission error as “the difference between the actual position of the output gear and the position it would occupy if the gear drive were perfectly conjugate.” Transmission error may be expressed as angular dis
22、placement or as linear displacement at the pitch point. Transmission error is caused by deflections, geometric errors, and geometric modifications.In addition to gear whine, other possible noise-generating mechanisms in gearboxes include gear rattle from gears running against each other without load
23、, and noise generated by bearings.In the case of automatic gearboxes, noise can also be generated by internal oil pumps and by clutches. None of these mechanisms are dealt with in this work, and from now on “gear noise” or “gearbox noise” refers to “gear whine”. MackAldener 2 describes the noise gen
24、eration process from a gearbox as consisting of three parts: excitation, transmission, and radiation. The origin of the noise is the gear mesh, in which vibrations are created (excitation), mainly due to transmission error. The vibrations are transmitted via the gears, shafts, and bearings to the ho
25、using (transmission). The housing vibrates, creating pressure variations in the surrounding air that are perceived as noise (radiation).Gear noise can be affected by changing any one of these three mechanisms. This dissertation deals mainly with excitation, but transmission is also discussed in the
26、section of the literature survey concerning dynamic models, and in the modal analysis of the test gearbox in Paper B. Transmission of vibrations is also investigated in Paper D, which deals with the influence of bearing endplay or preload on gearbox noise. Differences in bearing preload influence a
27、bearings dynamic properties like stiffness and damping. These properties also affect the vibration of the gearbox housing.1.3 ObjectiveThe objective of this dissertation is to contribute to knowledge about gearbox noise. The following specific areas will be the focus of this study:1. The influence o
28、f gear finishing method and gear modifications and errors on noise and vibration from a gearbox.2. The correlation between gear deviations, predicted transmission error, measured transmission error, and gearbox noise.3. The influence of bearing preload on gearbox noise.4. Optimization of gear geomet
29、ry for low transmission error, taking into consideration robustness with respect to torque and manufacturing tolerances.2 AN INDUSTRIAL APPLICATION TRANSMISSION NOISE REDUCTION2.1 IntroductionThis section briefly describes the activities involved in reducing gear noise from a wheel loader transmissi
30、on. The aim is to show how the optimization of the gear geometry described in Paper E is used in an industrial application. The author was project manager for the “noise work team” and performed the gear optimization.One of the requirements when developing a new automatic power transmission for a wh
31、eel loader was improving the transmission gear noise. The existing power transmission was known to be noisy. When driving at high speed in fourth gear, a high frequency gear-whine could be heard. Thus there were now demands for improved sound quality. The transmission is a typical wheel loader power
32、 transmission, consisting of a torque converter, a gearbox with four forward speeds and four reverse speeds, and a dropbox partly integrated with the gearbox.The dropbox is a chain of four gears transferring the powerto the output shaft. The gears are engaged by wet multi-disc clutches actuated by t
33、he transmission hydraulic and control system. 2.2 Gear noise target for the new transmissionExperience 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 unpleasant.Measurements showed that if the gear noise could be decrea
