• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.3
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• pp.92-99
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• 2021

An automatic transmission, which consists of several decks of planetary gear sets, provides multiple speed and torque ratios by actuating brakes and clutches (mechanical friction components) for connecting central members of the planetary gear sets. The gear set consists of the sun gear, the ring gear, and the carrier supporting multiple planet gears with pin shafts. In designing a new automatic transmission, there are many steps to design and analyze: gears, brakes and clutches, shafts, and other mechanical components. Among them, selecting thrust bearings that not only allow the relative rotation of the central members and other mechanical components but also support axial forces coming from them is important; doing so yields superior driving performance and better fuel efficiency. In selecting thrust bearings, the magnitude of axial forces on them is a critical factor that affects their bearing size and performance; its results are systematically related to the direction of the helical angle of each planetary gear set (a geometric design profile). This research presents the effects of the helical angle direction on the axial forces acting on thrust bearings in an automatic transmission consisting of planetary gear sets. A model transmission was built by analyzing kinematics and power flows and by designing planetary gear sets. The results of the axial forces on thrust bearings were analyzed for all combinations of helix angle directions of the planetary gear sets.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.5
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• pp.1-6
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• 2017

Gear tooth micro-geometry modifications include the intentional removal of material from the gear teeth flanks, so that the shape is no longer a perfect involute. If the gear shapes are perfect, then the gear tooth meshing is better, therefore the gears will transmit input torque in a more efficient manner without the generation of high frequency engine fluctuation noise. In this paper, we study tooth micro-geometry optimization of rear gear set in 2 speed planetary gear reducers. Analysis revealed problems which are need of modification. Based on the results, tooth micro-geometry was used to deal with load distributions on the rear gear set.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.7
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• pp.487-495
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• 2015

A generalized special program called planetary transmission analysis(here in after PTA) is developed to improve planetary gear noise in automatic transmission. PTA is capable of analyzing any typical one-degree-of-freedom automatic transmission gear train containing any number of simple, compound or complex-compound planetary gear sets. The kinematics module in PTA can compute the rotational speeds of gears and carriers and calculate the order frequencies to predict the planetary noise components. The power flow analysis module performs a complete static force analysis providing forces, moments, or torques of gears, bearings, clutches and connections. Based on the given type and number of planetary gear sets, the search algorithm determines all possible kinematic configurations and gear tooth combinations in a required set of gear ratios, while eliminating whole kinematic redundancies and unfavorable clutching sequences. By using PTA program, planetary internal speeds of new developed automatic transmission are early obtained; therefore, possibility of the noise problem could be predicted in early design stage. As implementing PTA in planetary gear NVH development procedure, planetary gear noise was successfully reduced by 10 dBA.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.3
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• pp.320-326
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• 2015

Despite the wide industrial applications of planetary gear trains, the relationship between the design parameters (tooth profile, carrier mass, etc.) and performance (strength, vibration, noise, etc.) remains poorly understood. A significant amount of research has focused on transmission errors, which are measurable performance indicators directly related to the design parameters. Herein, an experimental test rig for a single-stage planetary gear set built using digital angular encoders and gap sensors is described. To study the static and dynamic characteristics of this planetary gear train, the transmission errors and sun gear orbit are analyzed from the data measured under various levels of torque and speed. The transmission errors of the gear train decrease 40% when the speed increases from 30 to 600 rpm with an output torque of 39.2 Nm, and increase 22% when the output torque increases from 19.6 to 39.2 Nm with an input speed of 30 rpm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.261-262
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• 2011

Conventional automatic transmission system includes a hydrodynamic torque converter to transfer engine torque from an engine crank shaft to a rotatable input members, which are of complex design permitting them to serve several functions. These are clutches or brakes which couple the rotatable input member to member of a planetary gear set. The annulus gear for an automatic transmission is a monolithic gear having a set of gear teeth formed on an inner surface which is coupling with a set of planetary gear. In this study, the flow forming method is applied to the manufacturing of the annulus gear. This cold forming is proper method in order to manufacture dimensionally precise and round hollow components such as annulus gear. By pre-calculated amount of wall thickness reduction, the seamless tube of SAE1026 is compressed above its yield strength, plastically deformed and made to flow in several roll passes. According to this study, the desired geometry of the annulus gear can be achieved when the outer diameter and the thickness of the tube are properly decreased by compressed roll passes and the available material volume is easily forced to flow longitudinally over the shape of mandrel.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.253-261
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• 2014

In this paper, vibration analysis of power differential gear train for 2.5MW wind turbine system is analyzed. which system is composed of two planetary gear set, one helical gear set and main shaft that connected by flange. Planetary gear set, helical gear set, main shaft are modeled in MASTA program and housing, torque arm, carrier, flange components are modeling by finite element method. Each models are combined by component mode superposition. To analysis of natural vibration characteristic about 2.5MW wind turbine gear train was performed and check about critical speed with wind load, mass unbalance, angle misalignment excitation frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.544-545
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• 2012

In recent years, vehicle manufacturers have steadily developed fuel saving technologies such as multi-speed automatic transmission. With such a background, the Hyundai-powertech have developed the new 6-speed rear wheel drive(RWD)automatic transmission for FR vehicles. Despite having six-speed, it has the same number of planetary gears as a previously used five-speed automatic transmission and fewer brakes and one-way clutches than the 5 A/T, meaning that it is light, compact, and inexpensive. But, in addition to meshing this internal and external gear simultaneously and phase difference by the tooth contact point and the time difference occurs asymmetric and symmetric sideband noise and vibration caused by the modulation in the vehicle. In this paper presents a method for the design of the carrier phase difference by developing various theories and experiments for gear noise.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.5
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• pp.66-72
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• 2016

Gearboxes are mechanical components that transmit power by adjusting input and output speed and torque. Their design requirements include small size, light weight, and long lifespan. We have investigated the effects of carrier pinhole position error on the load sharing and load distribution characteristics of a planetary gear set with four planet gears. The simulation model for a simple planetary gear set was developed and verified by comparing analytical results with a putative model. Then, we derived the load sharing and load distribution characteristics under various pinhole position error conditions using the prototypical simulation model. The results showed that the mesh load factor and face load factor increased with the pinhole position error, which then influenced the safety factor for tooth bending strength and surface durability.

• Journal of Biosystems Engineering
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• v.41 no.3
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• pp.145-152
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• 2016

Purpose: This study aims to establish the effect of pinhole position errors in the planet carrier of a planetary gear set (PGS) on load sharing among the planet gears in the hydromechanical transmission (HMT) system of an agricultural tractor. Methods: A simulation model of a PGS with five planet gears was developed to analyze load sharing among the planet gears. The simulation model was verified by comparing i ts r esults w ith those of a model developed in a previous s tudy. The verified simulation model was used to analyze the load-sharing characteristics of the planet gears with respect to the pinhole position error and the input torque to the PGS. Results: Both simulation models had identical load magnitude sequences for the five planet gears. However, the load magnitudes on the corresponding planet gears differed between the models because of the different stiffnesses of the PGS components and the input torques to the PGS. The verified simulation model demonstrated that the evenness of load sharing among the planet gears increases with decreasing pinhole position error and increasing input torque. Conclusions: The geometrical tolerance of the pinhole position should be properly considered during the design of the planet carrier to improve the service life of the PGS and load sharing among the planet gears.

• Journal of Drive and Control
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• v.17 no.2
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• pp.19-27
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• 2020

The purpose of this study was to suggest design criteria for the HMT (hydro-mechanical transmission) of a 55 kW-class agricultural tractor, develop a simulation model, and evaluate its performance such as axle rotational speed, tractor speed, and power transmission efficiency. In this study, the HMT comprised a compound planetary gear and a HSU (hydro-static unit), and the compound planetary gear comprised two planetary gear sets. The HMT has three gear stages, and the maximum tractor speed was selected as 40 km/h. The simulation time was set at 2736 hours considering the lifetime of the tractor, and the simulation was performed for each gear stage at the engine-rated power conditions. As a result of the simulation, the axle rotational speeds for each gear stage were 39, 77, and 158 rpm, respectively. The range of tractor speed for each gear stage were 1.05-10.22 km/h, 10.74-20.17 km/h, and 20.70-41.40 km/h, respectively. The APE (absolute percentage gear) for the tractor's maximum speed between target value and simulation results were 2.20%, 0.85%, and 3.50%, respectively. Also, the power transmission efficiency for each gear stage were 0-75%, 72-81%, and 69-81%, respectively. The simulation results for the power transmission efficiency of the HMT were similar with the results of the previous research. This was a basic study on the development of the HMT for an agricultural tractor. In future studies, it is necessary to develop a tractor platform and evaluate the performance. The comparison between the simulation model and the HMT tractor should be performed.