How Torque Converters Work

If you are familiar with manual transmissions, you are aware that an engine and transmission are linked together by a clutch. A car wouldn’t be able to completely stop without killing the engine without this connection. The clutch that separates the transmission from the engine is absent in vehicles with automatic transmissions. They substitute a device known as a torque converter instead. Although it may not seem like much, there are a lot of fascinating things happening within.

Torque is created when a car’s engine crankshaft is turned (which is the energy you create by twisting something). Your car’s ability to accelerate depends on torque. A automobile moves more quickly the more torque it creates. A torque converter enables a vehicle’s engine to

Torque Converter Basics

How Torque Converters Work

An example of a fluid coupling is a torque converter, which enables the engine to rotate to some extent independently from the transmission. The amount of torque that passes through the torque converter when the engine is running slowly, as when the car is idling at a stoplight, is relatively minimal, so maintaining control of the vehicle only takes light pressure on the brake pedal.

While the car is stopped, pressing harder on the brake would be necessary to prevent it from moving if you were to push the gas pedal. This is due to the fact that applying more gas causes the engine to accelerate and to push more fluid into the torque converter, which increases the amount of torque sent to the wheels.

Inside a Torque Converter

How Torque Converters Work

The torque converter’s extremely sturdy casing contains four parts:

  • impeller
  • turbine
  • stator
  • transmission fluid

The torque converter’s casing rotates at whatever speed the engine is operating because it is bolted to the engine’s flywheel. Due to their attachment to the housing, the fins that make up the torque converter’s pump likewise rotate at the same rate as the engine. The torque converter’s internal connections can be seen in the cutaway below.

Among centrifugal pumps, the impeller in a torque converter is one. Similar to how a washing machine’s spin cycle throws water and laundry to the exterior of the wash tub, fluid is tossed to the outside when it rotates. A vacuum is produced as fluid is thrown to the exterior, drawing more fluid toward the center.

After that, the liquid enters the turbine’s blades, which are attached to the transmission. The turbine makes the transmission spin, which then transfers power to the driving wheels via shafts, differentials, and other components. The turbine’s curved blades can be seen in the graphic to the left. This implies that before the fluid leaves the center of the turbine, which it enters from the outside, it must reverse its direction. This shift in direction is what makes the turbine spin.

Regardless of whether the object is a car or a drop of liquid, you must apply a force to it in order to change its direction of motion. The force that turns the object must also be applied by something else, but in the opposite direction. Thus, the fluid spins the turbine as the turbine causes it to shift direction.

When the fluid leaves the turbine, it is travelling in the opposite direction from how it entered. The fluid leaves the turbine turning the opposite way that the engine and pump are turning. Allowing the fluid to reach the pump would slow down the engine and waste power. That is why a stator is a part of a torque converter.

In the part after this one, we’ll examine the stator in more detail.

The stator

How Torque Converters Work

The torque converter’s stator is located right in the middle of the device. Its responsibility is to divert the fluid coming back from the turbine before it reaches the pump once more. The torque converter’s efficiency is greatly increased as a result.

The stator’s extremely aggressive blade layout nearly totally changes the fluid’s direction. The transmission’s stator is connected to a fixed shaft by a one-way clutch located inside the stator (the direction that the clutch allows the stator to spin is noted in the figure above). Because of this configuration, the stator can only spin in the opposite direction from the fluid, which forces the fluid to alter its direction as it approaches the stator blades.

Once the car is moving, something a little tricky occurs. Both the impeller and the turbine spin almost equally fast at highway speeds (the pump always spins slightly faster). The stator is no longer required because the fluid has returned from the turbine and is entering the pump already travelling in the same direction as the pump.

The fluid continues to move in the direction that the turbine is rotating even though it is changed direction by the turbine and flung out the back because the turbine is spinning more quickly in one direction than the fluid is being pumped in the other direction. The ball would continue to move forward at 20 mph if you were standing in the back of a pickup truck driving at 60 mph (96 kph) and throwing a ball out the back at 40 mph (64 kph) (32 kph). The fluid is thrown out the back in one direction, but not as quickly as it was going to start with in the other, similar to what happens in a turbine.

At high speeds, the fluid actually hits the rear sides of the stator blades, causing the stator to freewheel on its one-way clutch in order to avoid getting in the way of the fluid’s flow.

Benefits and Weak Points of Torque Converters

The torque converter actually offers your automobile greater torque as you accelerate out of a stop, in addition to the extremely vital job of enabling your car to come to a complete stop without stopping the engine. The torque of an engine can be increased by two to three times thanks to modern torque converters. Only when the engine is spinning significantly more quickly than the transmission does this effect occur.

What is referred to as a high-stall torque converter may be installed in some performance applications of automobiles. This component will transmit power to the wheels at a far greater RPM than a typical street converter (revolutions per minute). As a result, the converter’s torque multiplier impact occurs while the engine is producing close to its max power, enabling it to accelerate quickly after starting. However, in regular traffic, this impact is undesirable.

The transmission rotates at a speed that is roughly 90% of the engine speed at higher speeds. However, the ideal speed for the gearbox and engine would be same, as this would prevent power loss and heat buildup in the unit. This contributes to the fact that vehicles with automated gearboxes occasionally have lower fuel economy than vehicles with manual transmissions.

Some automobiles include a torque converter with a lockup clutch to counteract this effect. This clutch locks the torque converter’s two halves together as soon as they reach operating speed, preventing power loss and guaranteeing that the engine and gearbox spin at the same speed. In order to maximize power delivery and match the effectiveness of earlier manual systems, many modern automatics have additionally added up to 10 forward gears.

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