Articles, Blog

Torque Converter, How does it work ?

Torque Converter, How does it work ?


Most of us enjoy the smooth and effortless feeling of driving in an automatic transmission car The driving is effortless because you don’t need to worry about gear changing, and you don’t have a clutch pedal to operate in An automatic transmission car the work of the clutch pedal is automatically done by a hidden component Which is truly an engineering marvel the torque converter. The torque converter can even multiply the torque. Let’s see how this purely mechanical device performs its tasks Assume you are driving along smoothly, and you have to apply the brakes When you press the brake pedal the vehicles drive wheels stop turning This means that the drive shaft and the Associated transmission should also stop spinning But here comes the issue by applying the brakes you are not stopping the engine So at the time of braking if the engine and transmission are mechanically connected This would lead to a serious mechanical failure or the engine will stall You need a motion isolator for this purpose. this motion isolator is the torque converter? The torque converter is able to efficiently isolate the engine rotation from the transmission at the time of braking In normal driving conditions it transfers the engine rotation and power to the transmission Let’s see how it works This is a really simplified torque converter. It is basically a pump and a turbine immersed in transmission liquid The pump is directly connected to the engine so it always turns at the engine speed The liquid surrounding the pump will be pushed outwards due to the centrifugal force and it’s pressure increases The rotation of the pump adds a swirl to the liquid leaving the pump The turbine sits near to the pump and the high energy fluid coming out of the pump turns the turbine The turbine is connected to the transmission This way the engine power is transferred to the transmission via the transmission fluid? More specifically this configuration is known as a fluid flywheel When we introduce a component called a reactor between the turbine and pump it becomes a torque converter One of the main duties of the reactor is to send the fluid from the turbine back to the pump efficiently We will discuss more functions of the reactor later With this configuration even if the transmission comes to a sudden halt it will not affect the engine rotation Slippage between the pump and turbine is allowed here since they are connected by the fluid During normal operation the pump will be able to transfer motion and power to the turbine It should be noted that the turbine turns at slightly lower rpm than the pump due to energy loss in the fluid This is a simplified torque converter But you will never find this kind of configuration in any actual torque converter The pump and turbine of an actual torque converter is shown here In an actual torque converter the pump sits near to the transmission And the turbine sits near to the engine Let’s give proper colors to the components for better understanding Rotation from the engine is transmitted to the pump with the help of a cover The turbine output Rotation is transmitted to the transmission using a central shaft However, why is this arrangement made more complex than the previous case the answer for this comes from mechanical rather than fluid mechanics For the efficient operation of a torque converter the pump and turbine should both rotate in line with the crankshaft centerline The pump is directly connected to the engine crankshaft, so that will always be centered However, the turbine is independent of this unit this means that a bearing has to be used between the turbine and the crankshaft as Illustrated in order to make sure the turbine is also centered to the crankshaft In the current configuration one can achieve this quite easily however in the previous configuration This is very difficult since the turbine is far away from the crankshaft Now you might be wondering why this device which isolates motion is named as a torque converter This is because one of the most important functions of this device is to multiply the torque as the vehicle starts to move Let’s see how the torque converter does this The reactor is connected to a stationary shaft via a one-way clutch this means the reactor will be able to turn in one direction But not In the opposite For ease of understanding let’s increase the spacing between the components Now consider the situation as the vehicle starts here the pump is spinning at the engine speed But the turbine speed is lower and is slowly increasing This means that the fluid which leaves the turbine travels almost axially as shown This fluid when it hits the reactor blades will try to spin the reactor as shown But the one-way clutch in the reactor prevents this motion So what happens is that the fluid will be diverted in the same direction as the pumps rotation due to the stationary reactor as shown? In short the pump which adds swirl to the flow receives an already swirled fluid This makes the work of the pump easier and a greater pressure addition happens across the pump this highly pressurized fluid generates an amplified torque at the turbine and thus the transmission and the vehicle receives a greater level of torque as the vehicle starts to move However as the turbine speed increases The fluid leaving the turbine becomes more inclined as shown and at one point of time the inclined flow hits the other side of the reactor blades The reactor is free to spin in this direction so the reactor spins in the same direction as the pump and the turbine You can see that the swirl generation of the pump Inlet is lesser than the previous case And the torque multiplication ceases Here the turbine will be rotating at almost 90 percent of the pump speed This is a brilliant design As the vehicle starts to move when the driver needs maximum torque The Torque converter Multiplies the torque when the turbine attains a threshold speed the torque multiplication automatically ceases Thus the reactor plays a crucial role at the vehicle start? But without the reactor the torque converter will not perform well even in normal operation Let’s see why You might have noticed that the blades of the turbine are curved They are curved almost 90 degrees to absorb maximum energy from the fluid This means the turbine blades will always force the fluid to leave in a direction opposite to the rotation of pump and turbine due to this even at hide turbine speed the fluid swirl at the turbine outlet will be minimum If we do not use a reactor this very low swirl will affect the performance of the pump and the whole torque converter very badly With the introduction of reactor the flow gets diverted again, and the pump receives the fluid with improved swirl Even in normal operation you will find that the turbine turns slower than the pump in a torque converter This is due to energy loss within the coupling fluid To eliminate such energy losses modern torque converters use a lock-up clutch By activating this clutch during the normal operation The turbine will be mechanically locked with the pump unit and they will turn at the same speed This eliminates energy loss due to the fluid friction Before winding up the video, let’s summarize the uses of this brilliant mechanical device Thank you for watching the video and don’t forget to be one of our patrons

Tagged , , , ,

12 thoughts on “Torque Converter, How does it work ?

  1. I thank Prof. John Kelly and Dr. Kyle for their technical inputs to this video. If you like our work, please support us at https://www.patreon.com/LearnEngineering .
    Prof. John Kelly's channel – https://goo.gl/7gpTzF
    Dr. Kyle's channel – https://goo.gl/txDKdK

  2. Good video but it would be better if it was black and white, with a bit of grains and the narrator would sone like a 1940s Milton Friedman.

  3. Insert "This is real clever but I would like to let everyone know I'll stick to my manual; therefore I am a superior being" comment here

  4. I imagine a lot of trial and error were factors when designing this, along with the automatic transmission. Otherwise they were just super geniuses.

Leave a Reply

Your email address will not be published. Required fields are marked *