2.5MW 풍력발전기 기어박스 치형수정

Purpose Crossed helical gears have point contact and their surfaces are subject to high surface stress. Contact stress and root tooth stress are the most common sources of failure in crossed helical gear. This paper aims to study the load-carrying capacity and performance of crossed helical gear teeth with different gear tooth profiles. To overcome defects and reduce the sensitivity to small shaft angle changes. The combined tooth profile is designed to reduce the bending stresses, contact stresses and tooth deflection, and prevent pinion failure in the gearbox. Design/methodology/approach The principle of the method is a line contact is introduced instead of a point contact between two teeth in mesh with each other. The tooth surface of the helical gear is designed and cut by a modified tool. Higher normal pressure angles like 25° and 35° are used. The modified involute is accomplished to eliminate interference between the teeth. Engineering software packages have been applied to generate all crossed helical gears gear profiles. The modification is compounding curves consisting of an epicycloid-involute-hypocycloid gear teeth profile generated by the cutter modified. Findings The stresses in the crossed helical gear teeth profile were reduced by increasing the normal pressure angle values. Using a 35° pressure angle the enhancement percentage in contact stress and teeth fillet region will be about 29.345% and 15.421%, respectively. The best enhancement in a gear’s resistance is the epicycloid-involute-hypocycloid gear teeth profile. The enhancement was 32.610% and 18.588%. The skew in line of action in skewed helical gear will be sensitive when the crossing angles are small. Their teeth surface tends to be easily worn out; however, the wearing process will be reduced by using a proposed gear teeth profile. Practical implications The gear teeth to be modified are cut by a shaper process. The modifying rack cutter of this study can be used as a reference for creating a different helical gears sample. The helical teeth surface is modified to become an envelope of the other. This makes an original point contact change into a line contact. The epicycloid-involute-hypocycloid gear teeth profile is preferred for a higher contact ratio and a large load capacity. This work explicitly introduces a new method of kinematic consideration to improve the load capacity of crossed helical gear. Originality/value This paper showed some novel results by the unique shape of the rack-cutter designed to generate different helical angles and different gear positions. In the future, it will make valuable contributions to the further development of the dynamic performance of a crossed helical gear system through the study in the field of using asymmetric teeth profiles of helical gears with tip relief as the manner to enhance the crossed helical gear performance. Investigation of crossed helical gear by applying a predesigned parabolic function of transmission error enables the absorption of linear discontinuous functions caused by misalignment.

<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>

Corrigendum: Correlation of Planetary Bearing Outer Ring Creep and Gear Load Distribution in a Full-Size Wind Turbine (J. Phys.: Conf. Ser.1452 012062)

Spur gears are widely used in the power transmission mechanism of several machines. Due to the transmitted torque, spur gears experience high stresses which could cause gear tooth failure by surface pitting or root fracture. Tip relief and other gear profile modification have been considered for reducing the induced stresses in the gear tooth. In this work, the influence of tip relief on stresses on a pair of identical spur gear was analyzed using commercial FEA software ANSYS, and formulae for estimating contact and bending stresses were derived. Three cases of gear sets were analyzed; a non-modified pair and another two sets with linear and parabolic tip relief profiles. The non-modified gear set frictionless contact stress was validated against the calculated AGMA pitting resistance, Hertzian contact stress and a reported contact stress value in the literature. The four methods agreed well with each other. Similarly, bending stress was also compared with the AGMA bending strength and Lewis bending stress for validation. Then, friction coefficient was varied from 0.0 to 0.3 with increment of 0.1. The gear contact stress increased up to 11% relative to the frictionless case, whereas bending stress decreased by 6%. Linear tip relief modification was carried out for increasing normalised tip relief values of 0.25 to 1.0 with increment of 0.25. The gear frictionless contact and bending stresses decreased by a maximum of 4% and 2%, respectively. Frictional contact stress increased by up to 7.1% and the bending stress is almost identical with the frictionless case. Parabolic tip relief was also carried out with similar normalised tip relief values. Frictionless contact stress decreased by 5% while frictional contact stress increased by up to 11.5% and the bending stress is also almost identical with the frictionless case. Finally, four formulae were introduced for estimating the contact and bending stresses for a tip modified spur gear.

<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>

Spur gear is used to transfer rotary motion between parallel shafts. The simplicity in its design is one of the advantages of the spur gear. However higher frictional force that is accumulated on the gear teeth will influence the spur gear performance. Many previous papers elaborated extensively on the contact stress in the spur gear but few of them gave the details on how friction affects the gear teeth. There are insufficient frictional effect data in the gear and thus should be regarded as an important research parameter. In this paper, the contact stress of spur gear has been evaluated with and without friction by employing the Hertz theory, AGMA standard and finite element method (FEM). The frictionless contact stress result has been validated with both the theoretical methods with minimum deviation. Frictional coefficient range of 0.0 to 0.3 was selected and the corresponding contact stress is directly proportional to the friction coefficient. The work also involves the variation of face width of the gear set under the influence of friction. The contact stress of spur gear was found to be inversely proportional to the face width.

We have successfully developed a tooth profile which enables a spur gear having zero relative curvature at contact points under the engagement through the concave/convex pattern of contact and further enables a single flank of the tooth profile to have the infinite number of points where the relative curvature and specific sliding are zero values. We have given a name of “LogiX” to this tooth profile. A W-N (Wildhaber-Novikov) tooth profi¨le has been known as that having the concave/convex pattern of contact. The tooth profile, however, is applied only to a helical gear due to its feature of a point contact. While, on the LogiX tooth profile, an improvement has been made so that a pair of spur gears having the tooth profile may contact each other through the concave/convex pattern of a line-contact which cannot be achieved by the W-N tooth profile. Therefore, the LogiX tooth profile has realized a spur gear whose surface durability is as high as that of the W-N tooth profile. Since the results of durability tests show slightly higher than an involute one, it is expected that a new type heavy duty gear of this tooth profile puts into practical use. Furthermore, the tooth profile will have the possibility of creating the new era in the history of tooth profile theory.

According to Jarvis March method and characteristics of non-circular gear's tooth profile, a numerical algorithm of non-circular gear's tooth profile based on Jarvis March has been proposed. This method can calculate the non-circular gear's tooth profile with the help of improved Jarvis March method. And improve efficiency and accuracy by simplify shaper cutter model and envelope process. So this method can calculate the non-circular gear's tooth profile accurately and efficiently. In order to detect the correctness and efficiency of this method, the method has been used to calculate the tooth profile's curve data of non-circular gear. In the end, good results have been obtained and indirectly verify the correctness and efficiency of this method.

Vibration-based updating of wear prediction for spur 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.

Dudley's Handbook of Practical Gear Design and Manufacture

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.

On a gear tooth surface, there may be some certain points which contact twice with its mating gear tooth surface. This phenomenon is called secondary action. In this paper, applying this phenomenon in cycloid drive, a new type of double-enveloping cycloid drive is generated based on gear geometry theory, and the torsional stiffness is calculated. The new conjugated tooth profile is composed by an external cycloid tooth profile and a new generated internal ring gear tooth profile. The main characteristic of the new tooth profile is that there are double contact lines simultaneously between on tooth pair in a certain meshing area. In this paper, firstly the generation method of the new conjugated tooth profile is present, and the meshing characteristics are investigated. Secondly, the torsional stiffness calculation model for double-enveloping cycloid drive is established. The normal stiffness, the arm length of the meshing force and the torsional stiffness are calculated. Finally, based on a numerical example, the calculation results are present, and the torsional stiffness of double-enveloping cycloid drive is compared with that of the conventional cycloid drive both on single tooth pair and whole gear mesh.

High power applications at high speed create contact problems, increase heat sink values and transmission error (TE) during gear meshing. Hence, analyzing the gear mesh including helix angle effect, the optimization in terms of contact pressure and the transmission error reduction are all crucial for high-speed applications. In this study, meshing characteristics including helix angle based on different approaches, optimization of spur gears pairs in terms of the transmission error and contact stresses obtained from improved analytical method besides transmission design tools are all investigated for high-speed aerospace applications. Results reveal that significant transmission error reduction could be achieved by applying tip relief starting from the highest-point of single tooth contact for spur gears in aerospace applications. Hence, the need for higher contact ratio by helix angle inclusion for smoother transmission could be compensated by using tip-relief modified spur gears in gearbox since the heat sink values also need to be minimized by using relatively lower contact ratio. Results obtained from the improved analytical method by directly considering gear geometry including gear foundation effects based on direct deformation–summation approach are found in between AGMA (American Gear Manufacturers Association) standard and ISO (International Organization for Standardization) standard results.

A comparative experimental research on the diagnosis of tooth root cracks in asymmetric spur gear pairs with a one-dimensional convolutional neural network