WORKING OF TORQUE CONVERTER.

Video on the working of torque converter: Don't Click Here:

This topic completely explains about the working of a torque converter and how torque multiplication happens.Click Here: Kerala Kitchen (Cookery channel)

Torque converters are used in automatic  transmission vehicles. It replaces the clutch which is used in the manual transmission vehicles. Automatic transmission helps the driver for a smooth drive by avoiding the usage for clutch pedal for gear changing. Torque converter is a fluid coupling, which utilizes the centrifugal force exerted in the transmission oil to transmit power from the engine to the gearbox. It multiplies the torque from the engine and functions as a combined clutch and infinitely variable reduction gearbox.--Technical Videos--

Which are the major components of a torque converter?

1.       Impeller (pump).
2.       Turbine.
3.       Stator.

Impeller (Input): It is a part of the casing itself, as shown on in the figure it stays opposite to the engine, the impeller works as a centrifugal pump when the torque converter rotates. Its weight is 10.5 Kg.  

Turbine (Output): It is the part of the torque converted when carried the torque produced by the engine to the rear wheels through the transmission. It is connected using a shaft to the shuttle reverser of the gear box and the drive from the gear box reaches the rear wheels through the propeller shaft and differential. Its weight is 3.5 Kg.

Stator: It is placed at the center of impeller and turbine, its function is to redirect the flow coming from the turbine to the impeller in a positive direction with  out slowing down the impeller, it will be explained detailed in the working. Its weight is 1.8 Kg.

Where is the torque converter mounted?

Torque converter is mounted between the engine and the gear box. As shown in the figure the casing of the torque convert,  with the turbine side is bolted to the Flywheel of the engine and the casing side fixed through the charging pump(crescent type pump) to the transmission.

How does a Torque converted works?

 Fig: 1

As it was mentioned earlier the torque converted is a fluid coupling (a concealed unit with fluid inside). It has impellers on one side and turbine on the other side with stator at the centre. As the torque converted is mounted on the flywheel, it rotates at the same RPM of the engine. When looking from the rear of the vehicle to the engine it rotates in the anti-clockwise direction. Due to this rotation, the fluid inside the torque converted acquires a momentum. It  gains a centrifugal force and the impeller works as a centrifugal pump which  throws the fluid through the veins at the casing of the impeller (“1” as shown in fig 1). This fluid comes and hits the turbine (“2” as shown in fig 1). As turbine is a free unit which can rotate it starts to rotate and the torque produced is carried out to the transmission through shaft connected to the turbine. This is how the torque produced by the turbine is transferred to the transmission.

If we monitor closely we can see that the fluid flow received by the turbine changes its direction when it passed thought fins (“3” as shown in fig 1) and direct it back to the impeller. If this reverse flow comes and hit the impeller it may slow down the impeller (“4” as shown in fig 1), if impeller slows down it will slow down the engine as it is mounted to the flywheel of the engine. To avoid this from happening we have a stator in place. The stator is so designed that it will again reverse the flow coming from the turbine to reach the impeller in a positive direction of the vanes of the impeller (“5” and “6” as shown in fig 2), which  will not slow down the impeller which results in a smooth working.

 Fig:2

Stator is a one way clutch, it rotates only in the direction of the flywheel, on the other direction it is locked. This is how a torque converted works.

How does torque multiplication happen?

It happens when the torque converted is stalled. That means when the engine is working and the turbine is locked or turbine staring to slow down compared to impeller torque multiplication happens. When we apply brake while engine is working the turbine is stopped as the shaft connected from the turbine to the shuttle reverser of the gear box is locked. This make the fluid coming from the impeller hits the turbine and again gets redirected by stator to the impeller, which results in the addition of velocity of the fluid flowing. In different cycles this velocity adds up resulting in the accumulation of torque on the turbine this results in torque multiplication (as the same with, when the speed of the turbine is reduced compared to the speed of the impeller the flow will get redirected through the stator to the impeller and again to the turbine this also result in torque multiplication due to velocity addition) So when the brake is released the accumulated torque is carried away by the shaft of the turbine to the transmission. This helps the vehicle to attain a higher speed when it moves from a stop or brake.

Advantages of torque converter:

1. Drivers comfort.  
2. Can attain a high speed from a stop or brake.
3. No mechanical bonding between engine and transmission therefore, the flexibility of the torque converted drive greatly reduces wear on the transmission, absorbing shocks and torsional vibration from engine.  
4. Engine cannot be stalled due to overloading as fluid coupling slips.  

Disadvantages of torque converter:

1. Mileage will be less.   
2. If turbine is stalled as the impeller is rotating, all the power is dissipated as heat.
3. If converted is stalled for more than 10 seconds continually for various cycles, it may result on the failure of the one way clutch of the stator due to over heating.

--Technical Videos--