• 한국정밀공학회지
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• 제13권10호
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• pp.36-45
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• 1996

The precise estimation of the reliability and life of the Ravigneaux planetary gear train used in an automatic transmission is necessary in order to enable accurate material and geometric properties to reliability distrobution and the number of load cycles at failure. These are critical for the proba- bilistic design of complex planetary gear system as Ravigneaux type particularly during various gear ratios. The Ravigneaux planetary gear train has five gears, such as a forward and a reverse sun gear, a short and a long pinion, and an annulus gear. In this paper, the Ravigneaux gear system is analyzed to figure out the reliablity distribution. i.e. the probability of survival in the system without its overhaul. First, the reliablity method based on the Weibull distribution is used in conjuction with the Palmgren's model to predict both the individual reliabilities of its components and the nimber of load cycles when the system failed. Then using the presented method, the life of the Ravigneaux gear system can be determined. Alwo the different design parameters such as tooth face width, material property, and Weibull exponent are applied and reached to optimal ones. Thus, the precise evaluation of the reliability and life of the Ravigneaux planetary gear train used in an automatic transmission can be effectively carried out.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.54-66
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• 1998

In a passenger car automatic transmission, the gear ratio is determined by the combination of clutches and brakes, and each element of th planetary gear set is rotated or held stationary by the action of them. In this study, to investigate the shift characteristics of automatic transmission, the equations of motion are derived from the dynamic model of Ravigneaux type planetary gear set and solved analytically. The shift characteristics of each element of planetary gera set during gear ratio change are investigated by considering the torques and velocities of input, reaction and output elements.

• 한국기계가공학회지
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• 제18권3호
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• pp.49-58
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• 2019

Automatic transmissions are standard equipment in most automotive vehicles because they provide smooth speed shifting and a compact design with multiple speed ratios. Their structure consists mainly of planetary gear sets as power-transmitting devices and brakes and clutches as shifting devices. Several forward and one reverse speed ratios are achieved by actuating shifting devices to connect gears, input and output shafts, and the transmission case. In the development of a new transmission, kinematic configurations reflecting the transmission concept design are required, and the ability of the new concept design to be assembled without any interference among the connections must be demonstrated. In this study, an assemblability analysis of the kinematic configurations of a Ravigneaux-type automatic transmission was conducted with an assemblable example of an 8-speed Ravigneaux-type automatic transmission.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.267-270
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• 2001

A lot of efforts have been made to analyze the performance of the vehicle equipped with automatic transmission through simulation. It might be necessary to understand the different types of transmissions, i.e., different power flows, for different models. If there is a module that can be applied to different types of automatic transmission, it could be helpful to transmission-related engineers. This study has started up from this idea. The common bond graph has been obtained from several types of the automatic transmission. The overall generalized equations and kinematic constraint equations have been derived using virtual power sources on common bond graph. They are used to derive state equations and constraints. These equations have been applied as an application to the vehicle equipped with two simple planetary gear set type of Ravigneaux gear type automatic transmission. The state equation, kinematic constraints, and dynamic constraints have been derived in every gear and shift operation using overall generalized equations and kinematic constraint equations. Simulations for constraint speed running, standing-start running, rolling-start running, and LA-4 mode have been conducted to analyze the performance of the vehicle powertrain using GVPS(Generalized Vehicle Powertrain Simulation) program wit pull down menus.