If you have ever driven the car with an automatic transmission, then you would know that there are two big differences between an automatic transmission and a manual transmission, the automatic transmission's primary work is to allow the engine to operate in it`s narrow range of speeds while providing a wide range of output speeds.
Without the transmission, cars will be limited to only one gear ratio, and that ratio would have to be selected to allow the car to travel at the desired full speed. If you wanted the top speed of 130 kph, then the gear ratio would be similar to 3rd gear in almost every manual transmission cars.
You have probably never tried driving a manual transmission car using only third gear. If you did, you would quickly find out that you had almost no acceleration when starting out, and at high speeds, the engine would be screaming along near the red-line. A car like this would wear out very quickly and would be nearly undriveable.
So the transmission uses gears to make more effective use of the engine's torque, and to keep the engine operating at an appropriate speed. When towing and hauling heavy objects, your vehicle's transmission can get very hot enough to burn up the transmission fluid. In order to save the transmission from serious damage, drivers who tow should buy vehicles equipped with transmission coolers.
The key difference between the manual and an automatic transmission is that the manual transmission locks and unlocks different sets of gears to the output shaft to achieve the various gear ratios, while in an automatic transmission, the same set of gears produces all of the different gear ratios. The planetary gearset is the device that makes this possible in an automatic transmission. the sun gear is locked and the planets driven by the planet carrier, the output is taken from the ring gear, achieving a speed increase.If the ring gear is locked and the sun gear is driven, the planet gears transmit drive through the planet carrier and speed is reduced.
With power input going to the
sun
gear and with the planet carrier
locked, the ring gear is driven,
but transmits drive in reverse.
To achieve direct drive without
change of speed or direction of
rotation, the sun is locked to the
ring gear and the whole unit turns
as one.
The same effect can also be achieved by locking the planet gears to the planet carrier.Most automatic gearboxes have three forward speeds, and use two sets of epicyclic gears.
The locking sequences of the epicyclic gear train are achieved by hydraulic pressure operating brake bands or multi-plate clutches.
The bands are tightened round the ring gear to prevent it turning, and the clutches are used to lock the sun gear and planets.
The correct sequence of pressure build-up and release is controlled by a complex arrangement of hydraulic valves in conjunction with sensors that respond to engine load, road speed and throttle opening.
A mechanism linked to the throttle - known as a kickdown - is used to effect a change-down for rapid acceleration. When you press down the accelerator suddenly to its full extent, a lower gear is selected almost instantly.
Most automatic gearboxes have an override system so that the driver can hold a low gear as required.
Without the transmission, cars will be limited to only one gear ratio, and that ratio would have to be selected to allow the car to travel at the desired full speed. If you wanted the top speed of 130 kph, then the gear ratio would be similar to 3rd gear in almost every manual transmission cars.
You have probably never tried driving a manual transmission car using only third gear. If you did, you would quickly find out that you had almost no acceleration when starting out, and at high speeds, the engine would be screaming along near the red-line. A car like this would wear out very quickly and would be nearly undriveable.
So the transmission uses gears to make more effective use of the engine's torque, and to keep the engine operating at an appropriate speed. When towing and hauling heavy objects, your vehicle's transmission can get very hot enough to burn up the transmission fluid. In order to save the transmission from serious damage, drivers who tow should buy vehicles equipped with transmission coolers.
The key difference between the manual and an automatic transmission is that the manual transmission locks and unlocks different sets of gears to the output shaft to achieve the various gear ratios, while in an automatic transmission, the same set of gears produces all of the different gear ratios. The planetary gearset is the device that makes this possible in an automatic transmission. the sun gear is locked and the planets driven by the planet carrier, the output is taken from the ring gear, achieving a speed increase.If the ring gear is locked and the sun gear is driven, the planet gears transmit drive through the planet carrier and speed is reduced.
With power input going to the
sun
locked, the ring gear is driven,
but transmits drive in reverse.
To achieve direct drive without
change of speed or direction of
rotation, the sun is locked to the
ring gear and the whole unit turns
as one.
The same effect can also be achieved by locking the planet gears to the planet carrier.Most automatic gearboxes have three forward speeds, and use two sets of epicyclic gears.
The locking sequences of the epicyclic gear train are achieved by hydraulic pressure operating brake bands or multi-plate clutches.
The bands are tightened round the ring gear to prevent it turning, and the clutches are used to lock the sun gear and planets.
The correct sequence of pressure build-up and release is controlled by a complex arrangement of hydraulic valves in conjunction with sensors that respond to engine load, road speed and throttle opening.
A mechanism linked to the throttle - known as a kickdown - is used to effect a change-down for rapid acceleration. When you press down the accelerator suddenly to its full extent, a lower gear is selected almost instantly.
Most automatic gearboxes have an override system so that the driver can hold a low gear as required.
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| AUDI AUTOMATIC TRANSMISSION |
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