• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.316-323
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• 2012

In order to meet the service life of planetary gearbox, a planet bearing, well known as the component with the highest failure rate, is designed. To predict the bearing fatigue life, ISO standard(ISO/TS 16281) is used, and the design parameters of the bearing are optimized using a parametric method. The whole planetary gearbox model is developed using a commercial software to calculate loads acting on planet bearings accurately. The results state that the designed bearings are satisfied with the life of 15,000hours, and the bearings that consist of 22rollers of 58mm have 1.6times longer life and better load sharing relatively than 22rollers of 28.5mm. Also, the increase in preload of taper roller bearings on the output pinion shaft prolongs the life of planet bearings regardless of roller's length.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.606-621
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• 2004

A dynamic analysis using a hybrid finite element method was performed to characterize the effects of a number of manufacturing errors on bearing forces and critical tooth stress in the elements of a planetary gear system. Some tolerance control guidelines for managing bearing forces and critical stress are deduced from the results. The carrier indexing error for the planet assembly and planet runout error are the most critical factors in reducing the planet bearing force and maximizing load sharing, as well as in reducing the critical stress.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1597-1606
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• 2003

Static analysis using hybrid finite element(FE) method has been applied to characterize the influence of position, runout and thickness errors of the sun, ring and planet on the bearing forces and critical tooth stress. Some guidelines for tolerance control to manage critical stress and bearing forces are deduced from the results. Carrier indexing error planet assembly and planet tooth thickness error are most critical to reduce planet bearing force and maximize load sharing as well as to reduce critical stresses. Sun and carrier bearing forces due to errors increase several times more than those of normal condition.

• Journal of Mechanical Science and Technology
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• v.18 no.11
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• pp.1978-1988
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• 2004

Hybrid finite element analysis was used to analyze the influence of bearing stiffness on the static properties of a planetary gear system with manufacturing errors. The effects of changes in stiffness were similar for most of the manufacturing errors. State variables were most affected by the stiffness of the planet ,bearings. Floating either the sun or carrier helps to equal load sharing and minimizes the critical tooth stress. The effects of a floating sun and carrier are similar, but it is not recommended that both float, because this can induce greater critical tooth stress. Planet bearing stiffness should be optimized. Both load sharing and critical tooth stress should be considered to determine optimal bearing stiffness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.198-205
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• 1998

In this paper, the dynamic characteristics of a star type epicyclic gear train have been analyzed. Nonlinear stiffness of a gear pair were obtained considering the bending and shear deformation, Hertz contact deformation, as well as tooth fillet deformation. Nonlinear stiffness coefficients and damping coefficients around the static equilibrium position were obtained by perturbation method. The loci of the planet gears and sun gear were estimated. Tooth meshing forces and bearing reaction forces were calculated. The effects of bearing clearance and oil viscosity on the gear behavior were also analyzed.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1775-1780
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• 2003

A hybrid finite element analysis was used to analyze the influence of ring gear rim thickness and spline number on the static properties of an epicyclic gear system with manufacturing errors. Both of these parameters affected the bearing force and critical stress. The effect of changes in the rim thickness on the load sharing between the gears depended on the type of manufacturing error. Ring flexibility improved the load sharing between planetary gears only in systems with planet tooth thickness or planet tangential errors; for other types of error, ring flexibility worsened the load sharing. To improve load sharing, rim thickness and spline number should be controlled within a specific range. The effect of the ring gear boundary condition was more apparent in a system with errors than in a normal system.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.29-35
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• 2013

The pitch reducer consists of several planetary gearsets, and they should have good load distribution over gear tooth flank and load sharing among the planets to improve the durability. This work investigates how bearing internal clearances influence both the load distribution over the gear tooth flank and the planet load sharing. A whole system model is developed to analyze a pitch reducer. The model includes non-linear mesh stiffness of gears, non-linear stiffness of bearings. The results indicate that the face load factor and mesh load factor decrease, and the fatigue life of output shaft bearings increase as bearing internal clearances of output shaft decrease. Therefore, the internal clearance of output shaft bearing must be considered when designing the pitch reducer for wind turbines.

• Korean Journal of Computational Design and Engineering
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• v.17 no.5
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• pp.312-323
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• 2012

Planetary gearing is a gear system consisting of one or more planet gears, revolving about a sun gear. While the planetary gear system has many advantages- for example, high power density, large reduction in a small volume, multiple kinematic combinations, pure torsional reactions, and coaxial shafting, it has not been widely used because of its high bearing loads, inaccessibility, and design complexity. It is also necessary to shift several pairs of gear profiles at a same time. Therefore, designing profile shifted planetary gear system is a difficult and know-how dependent job. This study provides a practical solution to design a profile shifted gear system by the procedural design scheme, and proposes a bearing integrated structure of the dual stage profile shifted gear system with a robust output end. A dual stage profile shifted gear system with the bearing integrated structure is manufactured by the proposed design scheme in this study. This gear system is verified that it is good enough to commercialize, because it has high performance with high gear ratio and robust output end against axial and radial directional runouts in a small space.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1949-1957
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• 2003

A hybrid finite element analysis was used to analyze the influence of ring gear rim thickness and spline number on the static properties of a planetary gear system with manufacturing errors. Both of these parameters affected the bearing force and critical stress. The effect of changes in the rim thickness on the load sharing between the gears depended on the type of manufacturing error. Ring flexibility improved the load sharing between planetary gears only in systems with planet tooth thickness or planet tangential errors; for other types of error, ring flexibility worsened the load sharing. To improve load sharing, rim thickness and spline number should be controlled within a specific range. The minimum rim thickness limit should be determined considering not only the critical stress but also the load sharing. The effect of the ring gear boundary condition was more apparent in a system with errors than in a normal system.

• Tribology and Lubricants
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• v.29 no.6
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• pp.378-385
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• 2013

An epicyclic gearing system is compact and lightweight. However, it is difficult to share the driving force equally because the system has closed gear trains with multiple driving points, and it always has geometrical errors in the elements. Thus, in the case of planetary gears, the first problem is how to distribute the load evenly to the numerous planets. The method widely used abroad for this purpose is to utilize the elastic deformation of the components of the structure. However, the deflection is very complicated, and it is very easy for vibration problems to occur because of the decrease in the natural frequencies. Therefore, to equalize the load on the planets, this paper discusses the principle and theory behind the functioning of a floating intermediate ring. This magnifies the displacement of a planet's center arising from the equilibrium of the load and the lubricating film pressure, which improves the compliance of the planets. The results show that load equalization of the planets is possible through this improvement in their compliance.