Automatic Transmission, How it works?

Summary

This video script delves into the intricate workings of automatic transmissions, focusing on the planetary gear set as the core mechanism. It explains how different speeds are applied to the sun and ring gears to achieve various gear ratios, utilizing clutch packs for power transmission. The script also covers the function of the transmission control unit and the torque converter, providing a comprehensive yet simplified explanation of high-performance automatic transmission systems.

Takeaways

• 🏎️ Automatic transmissions are popular in high-performance automobiles for their ease and reliability.
• 🌟 The working principles of automatic transmissions are based on the planetary gear set, which is a complex mechanism.
• 📚 Planetary gear sets consist of two inputs (ring and sun gears) and one output (planet carrier).
• 🔄 Different speeds applied to the inputs result in various output speeds, which is the core of automatic transmission operation.
• 🔄🔄 The ring and sun gears can rotate at the same speed, or in opposite directions, affecting the gear ratio and direction of the vehicle.
• 🌀 The speed variation is achieved by engaging a few clutch packs, which transmit different rotation speeds to the gears.
• 🔧 In an automatic transmission, there is no direct connection between the input and output shafts; an intermediate shaft and clutch packs are used for power transmission.
• 🛠️ Clutch packs lock the hub to the case, creating the simplest form of automatic transmission.
• 🔄 Applying different clutch packs to the planetary gear sets allows for achieving various gear ratios, including 1st, 2nd, and higher gears.
• 🔄🔄🔄 The combination of applying C1 and C4, for example, results in a higher output speed, demonstrating the gearing process for higher gears.
• 🔄🔄🔄🔄 A direct drive, like 4th gear, is achieved when the sun and ring gears rotate at the input shaft speed, facilitated by specific clutch pack applications.
• 🔄🔄🔄🔄🔄 The 3rd planetary gear set is used to achieve additional gear ratios, with the sun gear always connected to the input shaft.
• 🔄🔄🔄🔄🔄🔄 The reverse gear is achieved by applying the ring gear clutch, causing the sun gear to rotate in the opposite direction.
• 🤖 A transmission control unit decides when to apply which clutch pack, automating the gear shifting process.
• 🔄⚙️ A torque converter is necessary in automatic transmissions to isolate the engine rotation from the transmission when brakes are applied, using fluid coupling.

Q & A

What is the primary advantage of automatic transmissions in high-performance automobiles?

The primary advantage is that they offer easy and reliable driving with the ability to transmit different rotation speeds through a complex mechanism.

Which company's automatic transmission is used as an example in the video?

Allison Transmission is used as the example to explain the working principles of automatic transmissions.

What are the basic components of a planetary gear set?

A planetary gear set consists of a sun gear, a ring gear, and a planet carrier, which serve as two inputs and one output, respectively.

How does the output speed of a planetary gear set change when different speeds are applied to the inputs?

The output speed changes based on the rotation speed of the sun and ring gears. For instance, if the sun gear is rotating and the ring gear is stationary, the carrier spins, and if both gears rotate at the same speed, the mechanism moves as a single unit.

What is the role of clutch packs in an automatic transmission?

Clutch packs are used to transmit power by locking the hub to the case when pressed together, allowing for different speed variations to be achieved in the transmission.

How does the application of the 1st clutch pack affect the input and intermediate shafts?

Applying the 1st clutch pack connects the input shaft to the intermediate shaft, enabling power transmission between them.

What happens when both the 1st and 2nd clutch packs are applied together in an automatic transmission?

When both clutch packs are applied, the input shaft turns the sun gear, and since the ring gear is stationary, the output shaft rotates at almost one third of the input speed, achieving the 1st gear.

How is the 2nd gear achieved in an automatic transmission?

2nd gear is achieved by applying both C1 and C4 clutch packs, which causes the ring gear of the output set to turn, increasing the speed of the output planet carrier.

What is the purpose of the hollow shaft connected to the planet carrier?

The hollow shaft can be directly connected to the input shaft with a rotating clutch module, allowing for a direct drive in certain gear ratios, such as 4th gear.

How does the application of C1 and C2 clutch packs help achieve 6th gear?

Applying C1 and C2 connects the sun and ring gears directly to the input shaft, providing a high overdrive ratio at the output by giving the input rotation to the carrier while keeping the ring gear stationary.

What is the function of a torque converter in automatic transmissions?

A torque converter is necessary to isolate the engine's rotation from the transmission when the transmission is in gear and brakes are applied, using fluid coupling to accomplish this.