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Transient characteristics during gear ratio change including the disturbance of output torque have been important issues in the study of passenger car automatic transmission. In this paper, to investigate the transient characteristics during gear ratio change, a detailed dynamic model of the power transmission system of a passenger car focused on the automatic transmission was proposed and the governing dynamic equations were derived and solved. The results of simulation showed good agreements with the experimental data. It was proved that the suggested dynamic model is very useful to analyze the phenomena occurred during the speed ratio change.

The efforts to improve automatic transmission (AT) efficiency for vehicle fuel economy are constantly continuing. In an AT the oil pump is the largest power loss factor. Therefore the effect on fuel economy is very high. The AT oil pump system has structural contradictions (high pressure × high flow), and the efforts to improve these areas are concentrated. In this paper, a two oil pumping system was designed to improve the efficiency and performance of a 6 speed AT installed in a Hybrid Electric Vehicle (HEV) [1], and the improvement was confirmed by a prototype experiment. As a result of the experiment, two pumping system was shown to improve vehicle fuel economy while reducing noise and oil pressure vibration.

The banded microstructure of pearlite and ferrite in normalized alloy steel is susceptible to thermal distortion during carburizing process due to its unidirectional orientation parallel to rolling direction. The planetary gears with material of banded microstructure have been experienced in high thermal distortion during carburizing and quenching process and result in uneven surface hardness and effective case depth at the inside of pinion gear after honing. These defects played failure initiation site roles in durability test during development of new automatic transmission. The galling between the contacting components in severe lubricating system was the main failure mechanism. Double normalizing at 920 °C was designed to resolve the banded microstructure of normalized alloy steel. The microstructure and grain size of the double heated steel became equiaxed and fine due to homogenizing and recrystallization through double heat treatment.

It is well known that the entrained air in oil causes appreciable reduction in the stiffness of hydraulic systems. It makes the response delays of the systems and sometimes destroys the stability. Because the hydraulic systems used in most of automatic transmissions are operated in relatively low pressure and high temperature, it is very important to analyze the effects of the air included in automatic transmission fluid. However, it is hard to derive the generalized model to describe the effective bulk modulus theoretically or measure it in actual operating conditions of automatic transmissions. This paper reviews the previous studies of the air effects in hydraulic systems and the measurement techniques of the effective bulk modulus in operating conditions. Based on this work, the theoretical model with moderate complexity and the measurement technique of the effective bulk modulus considering entrained air effect at real operating conditions are suggested.

This paper shows the cause and the solution to the uncommon noise which happens ½ order component of engine rpm when a vehicle with automatic transmission has an air conditioning load and “drive” range load on the engine. By measuring cylinder pressure, main bearing cap vibration, engine mount vibration, and interior noise simultaneously, the cause of the noise can be proved by analyzing and comparing the data. The cause of the uncommon noise is bending vibration of the crank shaft. To solve the problem, one can change the crank shaft dynamics by reducing the mass of the damper pulley.

A comprehensive investigation was carried out in order to develop the idle sound quality for diesel V6 engine when the engine development process is applied to power-train system, which included new 8-speed automatic transmission for breaking down the noise contribution between the mechanical excitation and the combustion excitation. First of all, the improvement of dynamic characteristic can be achieved during the early stages of the engine development process using experimental modal analysis (EMA) & the robust design of each engine functional system. In addition, the engine structural attenuation (SA) is enhanced such that the radiated combustion noise of the engine can be maintained at a target level even with an increased combustion excitation. It was found that the engine system has better parts and worse parts in frequency range throughout the SA analysis. It is important that weak points in the system should be optimized.

Generally, the widely used hydraulic control system in automatic transmissions is pulse width modulation (PWM) type. It consists in a PWM solenoid valve and a reducing type second stage valve, so called pressure control valve (PCV), to amplify pressure or flow rate. In this study, the mathematical models of the PWM solenoid valve and the PCV with moderate complexity are proposed. Then, their behavior is analyzed from the steady state characteristics. Finally, we find that there are good matches between the dynamic simulation results and the experimental data.