Auto Tech 101: What is a Car Transmission? | Toyota

Summary

This video explains the essential role of vehicle transmissions in transferring engine power to the wheels. It covers various types of transmissions, including manual, automatic, and continuously variable transmissions (CVT), highlighting how each system optimizes engine power, speed, and fuel efficiency. The video also delves into advanced features like torque converters, hybrid CVTs, and engine braking. By comparing the functionality of different transmission systems, it emphasizes their importance in maintaining smooth driving performance and improving fuel efficiency in modern vehicles.

Takeaways

• 😀 Transmissions are crucial components that transfer engine power to the wheels, helping to keep the engine within its optimal RPM range.
• 😀 Engines need to maintain a specific RPM range to produce usable power. A transmission helps manage this balance by using different gear ratios.
• 😀 Gear ratios determine the number of rotations between two connected gears, affecting vehicle speed and effort, similar to how gears work on a bicycle.
• 😀 A transmission not only helps power the vehicle forward but can also help slow it down by using engine resistance when the accelerator is lifted.
• 😀 Manual transmissions require the driver to use a clutch and gear selector to shift gears, which prevents stalling and allows for control over gear selection.
• 😀 Automatic transmissions shift gears on their own and often include a torque converter, which multiplies engine torque using hydraulic fluid between two fans.
• 😀 The torque converter in automatic transmissions allows the vehicle to stop without stalling and can lock when torque multiplication is unnecessary for better efficiency.
• 😀 A Continuously Variable Transmission (CVT) replaces traditional gears with a flexible belt and pulleys, offering near-infinite gear ratios for smoother transitions.
• 😀 Some CVTs, like Toyota's Direct Shift CVT, add a physical first gear to improve initial acceleration response, followed by multiple simulated gear ratios.
• 😀 Hybrid vehicles use a Hybrid CVT to blend engine and electric motor power, improving efficiency and providing instant torque when needed.
• 😀 The Hybrid CVT also features a 'B' gear for engine braking, similar to lower gears in conventional transmissions, which helps when driving downhill.

Q & A

What is the primary function of a transmission in a vehicle?

The primary function of a transmission is to transfer engine power to the wheels while maintaining an optimal RPM range, ensuring that the engine operates efficiently without stalling or losing power.

Why can't an engine be directly connected to the wheels?

An engine cannot be directly connected to the wheels because it needs to maintain a specific RPM range to produce usable power. Without a transmission, the engine would either stall if RPMs fall too low or lose power if they get too high.

How does gear ratio affect the performance of a vehicle?

The gear ratio determines the balance between speed and power. A lower gear ratio (larger gear at the wheels) provides more torque and less speed, ideal for hills or starting from a stop. A higher gear ratio (smaller gear at the wheels) allows for faster speed with less torque, suitable for cruising.

What is engine braking, and when is it useful?

Engine braking occurs when the driver lifts off the accelerator and the engine naturally slows the vehicle down. This effect is enhanced by staying in a lower gear and is especially useful when traveling downhill to reduce the need for applying the brakes.

What is the key difference between manual and automatic transmissions?

A manual transmission requires the driver to manually shift gears using a gear selector and clutch, while an automatic transmission shifts gears on its own, based on vehicle speed and engine load, without requiring driver input.

How does a torque converter work in an automatic transmission?

A torque converter uses two fans (or impellers) filled with hydraulic fluid. One fan is driven by the engine, while the other drives the transmission. The fluid circulates between the two, multiplying the engine's torque, allowing the vehicle to move without stalling, even when stopped.

What is the purpose of the clutch in a manual transmission?

The clutch in a manual transmission disconnects the engine's flywheel from the transmission during gear shifts, allowing the driver to select a new gear without stalling the engine.

What is the difference between a conventional automatic transmission and a continuously variable transmission (CVT)?

A conventional automatic transmission uses fixed gears and planetary gears to adjust the torque and RPM, while a CVT uses a flexible belt and pulleys to provide near-infinite gear ratios for smoother acceleration and deceleration.

How does Toyota's Direct Shift CVT improve the driving experience?

Toyota's Direct Shift CVT addresses the sluggish response of traditional CVTs by adding a physical first gear that provides a more responsive start, followed by nine simulated gear ratios for a smooth ride across varying speeds.

What is a Hybrid CVT, and how does it differ from a standard CVT?

A Hybrid CVT combines planetary gears and electric motors to manage both engine and electric motor power. This setup allows for seamless power blending and enhanced efficiency, as well as the ability to run purely on electric power under certain conditions.