What Is Torque Converter?
Torque converters are types of fluid coupling that transfer rotational power from a prime mover to a rotating driven load, like in an internal combustion engine. In a vehicle with automatics transmissions, the torque converter connects the power source to the load.
Torque converters are doughnut-shaped internal engine component that is directly connected between the engine and transmission. Inside the torque converter, there are two series of curved blades, each facing the opposite direction.
It is usually located between the flexplate of the engine and the transmission. The equivalent place in a manual transmission would be the mechanical clutch. The torque converter is a device inside an automatic transmission housing set between the engine & the gears.
Essentially an advanced hydraulics fluid coupling, the torque converters transmit and multiplies engines torques while allowing the vehicles to come to a fulls stop without touching or moving the transmission. Earlier cars used non-locking torque converters, but most modern vehicles use lock-up torque converters.
The lock-up torque converter has a built-in locking clutch mechanism. Once the transmissions sense a specific speed or engine RPM, the torque converters will use the clutches to lock indirect connections between the inputs & output shafts for better efficiency.
Before the lock-up clutch was invented to maximize efficiency, we originally accepted the energy loss that occurs during the transfers of powers betweens the engines & transmissions due to slippage. Without the clutch to lock the torque converter, the turbine can still spin about 90 percent as fast as the impeller, but they don’t reach the same speed. Thus, energy loss.
How Does a Torque Converter Work?
It is a bit difficult to understand how a fluid can provide the power to move an object such as a vehicle. A pump helps achieve torque control which works by circulating fluid around the torques converters, which is determined by the rotation of the crankshafts.
Turbines are located in the housing and rotate when the pumped fluid comes into contact with the turbine blades. In this way, the torque being transmitted to the transmission through the input shaft can be measured. The torque converter housing is attached to the flywheel and rotates in the turbine housing at the same speed as the crankshaft.
The impeller or centrifugal pump effectively thrusts the transmission fluid into the ribs of the turbine, which in turn rotates or transmits torque to the transmission. The stator is the barrier that forces the fluid back to the turbine instead of the pump, increasing the efficiency of the system.
When vehicles are idling, the speed at which the transmission oil pumps into the turbine is slow, which means the engine is getting very little torque through the transmission. As the crankshaft spins faster and the flywheel spins at higher speeds, fluid moves faster from the pump to the turbines, forcing the turbine to spin faster, allowing more torques through the transmission.
It is important to note that the internals of the torque converter is still a mystery. Basic mechanics can be understood, but the complex calculations and engineering behind it are best understood by someone with an advanced understanding of fluid mechanics.
Parts of Torque Converter:
#1. Impeller or Pump
Impellers are connected to the housing and the engine shaft. It has curved and angled vanes. It spins with the engine speed and has automatic transmission fluid. When it rotates with the engines, the centrifugal force moves the fluid outwards.
The blades of the impellers are designed in such a way that it directs the fluid towards the turbine blades. It acts as a centrifugal pump that sucks the fluid out of the automatic transmission & delivers it to the turbine.
stators are located between the impeller and the turbine. The main function of the stators is to direct the fluid returning from the turbine so that the fluid enters the impellers in the direction of its rotations. As the fluid enters the direction of the impeller, it multiplies the torque.
So changing the direction of the stator fluid helps in torque multiplication and allows it to enter the direction of impeller rotation. Stators change the direction of the fluid by about 90 degrees. The stator is mounted with one-way clutches that allow it to rotate in one direction and stop its rotation in the other directions.
The turbines are connected to the transmission system of the vehicles. And the stator is placed between the impeller and the turbine.
The turbine is connected to the input shafts of the automatic transmission. It is present on the side of the engine. It also has curved and angled blades. The blades of the turbines are designed in such a way that they can completely change the direction of the fluid falling on its blades.
It is the change in the directions of the fluid that forces the blades to move in the directions of the impellers. As the turbine spins, the input shaft of the transmission also rotates and makes the vehicle move. There is also a lock-up clutch behind the turbine.
The lock-up clutches come into plays when the torque converter reaches the coupling point. Eliminates lock-up losses and improves converter efficiency.
Working Principle of Torque Converter:
To understand the working principles of the torques converters, let’s take two fans. One fan is connected to powers sources, & the other is not connected to the power source. When the firsts fan connected to the power sources starts running, air flows from it to the second fan, which is stationary.
The air coming out of the first fan hits the blades of the second fan, and that too starts rotating at almost the same speed as the first fan. When the second fan is turned off, it does not stop the first one. The first fan keeps spinning. On the same principle, the torques converters works.
In that, the impeller or pumps acts as the first fan, which is connected to the engine, & the turbine acts as the second fan, which is connected to the transmission system. When the engine runs, it spins the impeller, and due to centrifugal force, the oil inside the torque converter assembly is directed towards the turbine.
As it strikes the blades of the turbines, the turbine starts rotating. This rotates the transmission system and moves the wheels of the vehicle. When the engine is stopped, the turbine also stops spinning, but the impeller attached to the engine continues and does not kill the engine.
It has three phases of operation
During the vehicle’s stall condition, the engine is applying power to the impeller, but the turbine cannot spin. These occur when the vehicles are stationary, and the driver has put his foot on the brakes pedals to prevents it from moving forward.
The maximum multiplication of torque occurs during this condition. A driver takes his foot off the brakes pedals & depresses the accelerator pedal, the impeller begins to accelerate, and this sets the turbine to run.
In these situations, there are big differences between the speed of the pump and the turbine. The impeller speed is much higher than the turbine speed.
During acceleration, the speed of the turbine keeps increasing, but still, there is a big difference between the speed of the impeller and the turbine. As the turbine speed increases, the torque multiplier decreases. The torque achieved during a stall condition is less than the multiplier during the acceleration of the vehicle.
This is a condition when the turbine has achieved about 90 % of the impeller speed, and this point is called the coupling point. The torque multiplier seizes and becomes zero, and the torque converter behaves like a simple fluid coupling. At the coupling points, the lock-up clutch comes into play & locks the turbine to the converter’s impeller.
This keeps the turbine and impeller moving at the same speed. The lock-up clutches engage only when the coupling points are achieved. During coupling, the stator also begins to rotate in the direction of the impeller and turbine rotation.
Types of Torque Converter:
#1. Single-Stage Torque Converters
The beauty of single-stage converters is their strict, reliable simplicity. Every converter basically consists of three elements: turbine, stator, and impellers. The single-stage converter comes in two types of housing – stationary & rotating.
Depending on the models, single-stage torques converters have a variety of capabilities: Simplex single-stage converters with PTO drives are ideals for applications with power-shift transmissions and driving-assisted hydraulic pumps.
High torque ration converters with stable housing have exceptional hoisting and lowering capabilities. Type Four hydraulic converters are specifically designed for the oil and gas industry.
#2. Three Phase Torque Converters
Three-stage torque converters employ three rings of turbines blades, as wells as two sets of reactors or stator blades. The effect of these designs is increased torque – up to five times the amount of engines output torque, in fact, when the engines are at a stall.
Depends on the specifics design, the three-phase converters are rated for ranges of the engine, including 335 hp at 2400 rpm, 420 hp 2200 rpm, & 580 hp at 2,200 rpm. A three-stage converter also comes with both stationary & rotating housings.
Torque Converter Replacement Cost:
More of the above symptoms, your torque converter may not be working properly. Repairs can cost more than replacing them. Therefore it is necessary to see a mechanic/technician. If you plan to do the work yourself, the estimated repair cost is between $150 and $500. Repair shops charge between $600 and $1000 to replace a torque converter.
The torque converter itself is relatively inexpensive (between $150 and $350 depending on the vehicle), but it takes 5 to 10 hours of work because the transmission would have to be removed to replace the torque converter. Also, the fluid should be flushed/changed, which may or may not be included in the price the store will give you.