Torque converter operation

If you've read anything about 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 link. However, automatic gearbox vehicles lack a clutch that would normally separate the transmission from the engine. Instead, they make use of a torque converter, a remarkable machine. Although it may not seem like much, there are a lot of fascinating things happening within.

This article will explain why torque converters are necessary for automatic transmission vehicles, how they function, as well as some of its advantages and drawbacks.

What Is Basic?

Cars with automated gearboxes require a mechanism to let the engine to turn while the wheels and gears in the transmission halt, much as vehicles with manual transmissions. A clutch is used in manual transmission vehicles to entirely decouple the engine from the transmission. Automobiles with automatic transmissions employ torque converters.

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

While the automobile is stopped, pressing more 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.

A torque converter's inside

The torque converter's extremely sturdy enclosure contains four parts, as indicated in the illustration below:

• Pump
• Turbine
• Stator
• Transaxle fluid

The torque converter's casing rotates at whatever speed the engine is operating since it is attached 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 may be seen in the cutaway below.

The centrifugal pump used within torque converters is one of these pumps. 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. Your automobile is essentially moved by the gearbox, which is spun by the turbine. The turbine's curved blades are seen in the graphic below. This implies that before the fluid leaves the center of the turbine, which it enters from the outside, it must reverse its course. This shift in direction is what makes the turbine spin.

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

When the fluid leaves the turbine, it is travelling in the opposite direction from how it entered. You can see from the arrows in the above diagram that the fluid leaves the turbine turning the opposite way that the pump (and engine) are spinning. 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.

A Stator

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 stationary 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 automobile is underway, something a little problematic occurs. There is a moment where the pump and the turbine virtually spin at the same speed, which is roughly 40 mph (64 kph) (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 rear because the turbine is spinning more quickly in one direction than the fluid is being pushed in the other direction. The ball would still be travelling forward at 20 mph if you were standing in the back of a pickup truck moving at 60 mph and flung it out the rear at 40 mph. 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.

Advantages and Drawbacks

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

When traveling at greater speeds, the engine and transmission finally move at almost the same pace. The gearbox should, however, ideally go at the exact same speed as the engine because any variation in speed loses power. This contributes to the fact that vehicles with automated gearboxes have worse 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 slippage and enhancing performance.

Check out the links on the next page for additional details about torque converters and related subjects.