Automatic transmission questions

1. What is a fluid coupling? Give an example 
It is a two member drive coupling that are not physically connected but are facing each other enclosed in a shell. They are made up of a Impeller and a Turbine which transfers hydraulic fluid to the transmission. A torque converter is a Fluid coupling without the Stator.

2. What is the name given to a hydraulic coupling that increases torque?
Torque converter

3. Name the main parts of a torque converter
Impeller
Turbine
Stator

4. Explain the operation of each part of the torque converter
Impeller - The engine driven input, spins the hydraulic fluid in such a way to the Turbine
Turbine - Connected to the input of the transmission. The amount of fluid it receives from the Turbine determines how fast/slow it rotates the transmission.
Stator - Located in the centre of the torque converter. Redirect fluid returning from the Turbine before it hits the Impeller

5. Describe how torque is increased by the torque converter
A Stator is used. When fluid leaves the Impeller it is picked up by the Turbine but the fluid that doesn't pass through hits the Turbine and shoots back to the Impeller hitting it in the opposite direction its rotating causing the Impeller to slow down and slowing down the engine so there is potential that has just been lost. A Stator redirects the fluid that the Turbine rejects and because the shape of the vanes it causes the fluid to hit the Impeller in the direction its rotating acting with the Impeller and not against it therefore not loosing potential.

6. Explain the operation of the stator
The Stator is in the centre of the Impeller and Turbine. Its vanes are curved opposite to the Turbine and its job is to redirect the fluid returning before it hits the Impeller so the fluid ends up entering the Turbine in the same way its rotating.

7. What is rotary flow?
This is the circular flow that follows the rotation of the Torque converter.

8. What is coupling point?
Occurs when the speed of the Impeller and Turbine are very similar usually due to the vehicle being driven at a constant speed. This is the coupling point which means the stator must be able to freewheel in a clockwise direction. If this doesn't happen it would reduce the flow of fluid and slow down the vehicle.

9. What is meant by vortex flow?
This is a spiralling flow of the fluid inside the torque converter and continues as long as there is a difference in speed of the Impeller and Turbine.

10. Explain how a one way clutch works in the converter?
A one way clutch is attached to the Stator inside the Torque converter. It allows the Stator to rotate in the same direction as the Turbine. If the Stator tries to rotate in the other direction the one way clutch locks it in place to prevent it from doing so.

11. What is the purpose of a torque converter
To transfer the torque of the engine to the transmission and can either multiply the torque produced from the engine or act as a fluid coupling. It also smooths out engine rotation and can help to absorb vibrations from the engine.

12. Why do some converters have a clutch?
To prevent the Stator from rotating in the wrong direction the one way clutch locks it in place.

13. Explain how a lock up clutch works
A lock up clutch is used to lock Turbine to the converter housing which provides a direct drive from the engine to the transmission like a manual clutch. This reduces fuel consumption and provides a one to one drive.

14. What does a servo do in the transmission?
A servo is a spring loaded assembly that activates and releases the front and rear bands when shifting gears.

15. What is meant by torque multiplication?
The speed different between the Impeller and Turbine.

16. What does a band do in the transmission?
Bands connect and disconnect components in the transmission. They wrap around sections of the gear train and are attached to the housing. Hydraulic cylinders inside the case of the transmission actuate the bands.


Reference pages:
http://www.autoshop101.com/
https://www.google.co.nz/
http://www.howstuffworks.com/
http://moodle.unitec.ac.nz/