Had you ever asked yourself what a torque converter is? An hydraulic torque converter is a type of fluid coupling which transfers rotating power from an original mover into a driven load. This is mainly seen today in vehicles with automatic transmissions in which the torque converter acts as the connecting link from the power source to the load. One of the key characteristics of the torque converter is its ability to multiply to work when the output rotational speed is that such a level that the fluid coming off of the vanes of the turbine are deflected off the stator while it’s locked against a clutch, creating a reduction gear.
The theory of operation behind torque converters originate with the equations of motion, most notably Leonhard Euler’s turbo machine equation. There are at least three rotating elements inside of the torque converter which include the turbine, the impeller, and the stator. The turbine is driven mechanically by the prime mover, also known as the impeller which drives the load, and finally there is the stator which alters the flow of oil returning from the turbine to the impeller. The operation wing of the torque converter includes three separate stages. The first of which is the stall which includes the prime mover applying power to the impeller however, the turbine is unable to rotate. While in the stall stage the torque converter can produce maximum torque multiplication but there needs to be sufficient power from the input for the torque to be useful. The second stage of operation is acceleration. In this stage the load is accelerating however, there’s still a relatively large difference in the impeller and turbine speed. While in this stage the converter can produce torque multiplication that is less than what it would be under stall conditions. Finally, the last stage of operation for the torque converter is coupling. In this stage the turbine is at approximately 90% of the rotation speed of the impeller. There’s no more torque multiplication and the torque converter is now acting like a fluid coupling. In this stage there tends to be an improvement in fuel efficiency.
As far as hydraulic systems go, the most common form of torque converters can be located in automotive transmissions as the hydrokinetic device. There are also mechanical systems such as the continuously variable transmissions (CVT). Torque converters are used today not only in automatic transmissions on cars busses or trucks, but it is also used on marine propulsion systems and in industrial power transmission (railway locomotives).
According to The Lansing Post, the time period from 2018-2022 will be fruitful for torque converters and how they perform in relation to the market. The currently trends are that there are an increasing number of gears that able to cover a wider range of ratios for higher torque and power performance. The Lansing Post is able to be found online and provide the full in-depth analysis on torque converters.