Table of Contents
A torque converter is a type of hydraulic coupling used to transfer rotating power from a vehicle’s engine to the transmission. Replaces a mechanical clutch in an automatic transmission. The torque converter is a type of hydraulic coupling used to transmit more torque to the shaft driven by a prime mover such as an engine.
The transmitted torque can be greater or less than the input torque. Multiplying the torque is the key feature of the torque converter. The torque on the driven shaft can achieve three times the torque available in the motor shaft.
Impeller/pump: inlet part driven by a prime mover
Turbine: the outgoing part that drives the load
Stator: The stator is approximately half the diameter of the impeller or turbine. It is the reaction element of the torque converter. It is positioned between the impeller and the turbine so that it can redirect the flow of oil in the same direction as an impeller.
1. Stall: During the stalled (stopped) condition of the vehicle, the engine is applying power to the impeller but the turbine cannot rotate. This happens when the vehicle is stationary and the driver has kept his foot on the brake lever to prevent it from moving. During this condition, the maximum multiplication of the couple takes place.
When the driver removes his foot from the brake lever and presses the accelerator lever, the impeller starts moving faster and this causes the turbine to move. In this situation, there is a greater difference between the speed of the pump and that of the turbine. The speed of the impeller is much greater than the speed of the turbine.
2. Acceleration: During acceleration, the speed of the turbine continues to increase, but there is still a big difference between the speed of the impeller and that of the turbine. As turbine speed increases, torque multiplication is reduced. During the acceleration of the vehicle, the multiplication of the torque is lower than that obtained during a stall condition.
3. Coupling: This is a situation where the turbine has reached about 90% of the impeller speed and this point is called the coupling point. The torque multiplication freezes and goes to zero and the torque converter behaves just like a simple hydraulic coupling. At the coupling point, the lock-up clutch comes into play which locks the turbine to the impeller of the converter.
This causes the turbine and impeller to move at the same speed. The locking clutch engages only when the coupling point is reached. During coupling, the stator also begins to rotate in the direction of rotation of the impeller and turbine.
Advantages of Hydrodynamic Torque Converter
- Produces maximum torque compared to the clutch equipped vehicle.
- Removes the clutch pedal.
- Facilitates the work of driving a vehicle.
Disadvantages of Hydrodynamic Torque Converter
Its fuel efficiency is low compared to the manual transmission vehicle.
Application of Hydrodynamic Torque Converter
The torque converter is used in the vehicle equipped with an automatic transmission. It is also used in industrial power transmissions such as conveyor belt drives, winches, drilling rigs, almost all modern forklifts, construction equipment and railway locomotives.
It is used in marine propulsion systems.