Automotive Power Transmission Systems

4Torque Converters

4.1 Introduction

The invention of fluid couples, over a hundred years ago, was credited to H. Foettinger [1]. The fluid couple, with two elements, the impeller as input and the turbine as output, was later improved by adding the reactor between the two elements to become the torque converter. These hydraulic devices were first applied in the driving systems of ship propellers. The development of torque converters for applications in automotive powertrains dates back to the 1920s [1]. In the US automotive industry, fluid couples were already being applied in the 1930s in transmissions for production passenger cars and city buses [2]. The application of torque converters in automatic transmissions of passenger cars started to take off in the mid 1940s. By the late 1940s, automatic transmissions with torque converters were already in mass production [3,4]. The market demand for family cars grew rapidly in the booming economy after WWII, and this called for the development of automatic transmissions for passenger automobiles that would offer comfort and operation easiness. Torque converter, due to its input and output characteristics, proved to be a perfect fit between the engine output and the transmission input. The application of torque converters in the automotive industry was so widespread that more than 70% of passenger automobiles sold in 1960 in the USA were already equipped with automatic transmissions with these devices [5]. It can be stated that torque ...