Torque Converter Working, Principle, Main Parts and Application

Torque Converter Working, Principle, Main Parts and Application

A torque converter is a type of fluid coupling used for transferring rotating power to the transmission from the motor. It is achieved in an automatic transmission by a hydraulic clutch. The main function is to ensure that the load is separated from the main source of power. It is situated between the motor and the engine. It has the same feature as a handheld clutch. As the clutch separates the engine from the load when it stops, in the same way it also isolates the engine from load and keep engine running when vehicle stops.Its main functions are:

1. It transfers the power from engine to the transmission input shaft.
2. It drives the front pump of the transmission.
3. It isolates the engine from the load when the vehicle is stationary.
4. It multiplies the torque of the engine and transmits it to the transmission. It almost doubles the output torque.

Working Principle

Let's take two fans to grasp the torque converter operating theory. One fan is connected to the power supply and the other is not power supply connected. The air from it moves to the second fan which is stationary when the first fan associated with the power source starts to move. The air of the first ventilator hits on the second fan's blades and also almost at the same pace begins spinning to the first. The first fan starts when the second fan is stopped. The fan continues to revolve.

The torque converter operates according to the same concept. The pump functions as a first ventilator connected to the engine and the generator serves as the second ventilator connected to the transmission system. When the engine is working it rotates the wheel and the oil inside the torque converter is guided to the turbine because of its centrifugal power. The engine starts to spin as it reaches turbine blades. It rotates the transmission system and pushes the vehicle's wheels. The engine also starts spinning when the motor ends, but the drive connected to the motor continue to move and prevents the kill of the motor.

Main Parts

The torque converter has three main parts

1. Impeller or Pump

The rotor is linked to the cabinet and to the box connected to the motor shaft. It's been bent and twisted. This rotates at motor speed and consists of automatic fluid transfer. The centrifugal force causes the fluid to shift outward when it rotates with the engine. The blades are so designed that the fluid is directed towards the blades of the turbine. It acts as a centrifugal pump which absorbs and transfers the fluid to the turbine through the automatic transmission.

2. Stator

The stator is between the turbine and the impeller. The stator's principal task is to direct the returning fluid out of the turbine to the impeller in the direction of its rotation. When the fluid reaches the impeller stream, the torque is compounded. The stator then helps to increase the torque by changing the direction of the fluid and allows it to reach the direction of rotation of the impeller. The stator shifts almost 90 degrees in the direction of the stream. The stator is installed with a one-way embrace which enables it to rotate in one direction and avoid rotation in another. Turbine is attached to the vehicle's transmission system. And between the turbine and the roller is the stator.

3. Turbine

Turbine is mounted to the automatic transmission input shaft. It's on the side of the car. There are bent and pointed blades as well. The turbine blades are designed so that the direction of the fluid which hits its blades can be modified altogether. The change of direction of the fluid causes the blades to shift towards the impeller. The Turbine also rotates and lets the vehicle shift while the shaft of the motor is spinning. The turbine also has a rear sealing clutch. When the torque converter hits a coupling point, the clutch comes into play. The lock-up eliminates losses and increases the converter's performance.

Working of Torque Converter

It has three stages of operations
1. Stall: The engine uses power to the impeller when the vehicle is stall (stop), but the turbine can not rotate. This is when the car is stationary and the driver has kept his foot on the brake paddle so that it does not move. Maximum torque multiplication takes place during this condition. The impeller moves faster as the driver removes the base from the brake paddle and releases the accelerator paddle, allowing the motor to roll. There is a greater difference in the pump speed from the turbine in this situation. The speed of the rotor is significantly higher than that of the turbine.
2. Acceleration: During acceleration, the speed of the turbine continues to rise, but the impeller and turbine speed also differ greatly. The torque multiplication is decreased as the turbine speed increases. The torque multiplication is less than under standing conditions when the engine is accelerated.
3. Coupling: This happens when the turbine reaches a speed of about 90% of the impeller, which is known as the coupling point. The torque multiplication is null and negative and the torque converter is compared to a simple fluid relation. The locking clutch comes in at the coupling point and locks the turbine to the converter's impeller. This enables the turbine and drive to move at the same speed.  Only when the point is reached is the clutch locked up. The stator also begins to rotate towards the rotation of the rotor and of the turbine during the coupling.
1. The maximum torque multiplication takes place during stalling condition.
2. The stator remains stationary before coupling point and helps in the torque multiplication. As the coupling attained, stator stops torque multiplication and starts rotating with the impeller and turbine.
3. Lock up clutch engages when coupling point is achieved and removes the power losses resulting in increased efficiency.


  • It produces the maximum torque as compared with the vehicle equipped with clutch.
  • It removes the clutch pedal.
  • It makes the job of driving a vehicle easier.


  • Its fuel efficiency is low as compared with the vehicle with manual transmission.


  • The torque converter is used in the vehicle that is equipped with the automatic transmission. It is also used in industrial power transmission such as conveyer drives, winches, drilling rigs, almost all modern forklifts, construction equipment, and railway locomotives.
  • It is used in marine propulsion systems.

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