Good afternoon friends, welcome back to my website. In the last post, I have written about Manual Transmission and in this post, I would be covering Automatic Transmission. So, basically, an automatic transmission is a type of transmission which free driver or computer from a headache or fun (for some person may really like manual) of changing gears and pressing the clutch pedal.
So, how is this achieved? The answer to this question lies in the beauty of working mechanism of this type of transmission. Before I explain about its working the thing you should know is what “torque converter” in the automatic transmission is.
So, how is this achieved? The answer to this question lies in the beauty of working mechanism of this type of transmission. Before I explain about its working the thing you should know is what “torque converter” in the automatic transmission is.
torque converterSo, basically what is the torque converter? As you have seen clutch plays an important role in transmitting power from engine to the gear box. So, as clutch does the job in manual transmission same work is done by torque converter in the automatic transmission. Basically, it's a fluid coupling (coupling it a way of connecting two power transmitting shafts). In this, we have an impeller, a turbine, and a stator. The impeller is connected to the engine flywheel, turbine to the output gearbox and stator as intermediate part between turbine and impeller. Basically what it do it multiplies the torque output from the engine by the help of stator and fluid oil placed in the housing of the torque converter. To understand it in details I have attached a Youtube Video please see to it for detailed working. | |
working of aut0matic transmission
So, now we basically come to the working of the automatic transmission. So, in an automatic transmission, we have various multi-plate clutches and planetary gear system (as can be seen on the picture on your right). This combination of the gear and clutches with torque converter make automatic transmission works. So, let me start with the working of this system. When the vehicle is standing torque converter transmit zero power from engine to the gearbox hence vehicle does not move. But as soon as you press your accelerator pedal torque get multiplied and start to get transmitted to gear box using a torque converter. Gearbox consists of many clutches which engages and disengages according to the speed of the vehicle. |
So, now power is available to the gearbox so, it the time for it to engage first gear. So in first gear, the input shaft get power and small sun gear starts rotating and with it, ring gear also rotates but planet gear get locked and rotate about its axis only. Since the output is taken from the ring gear thus maximum gear ratio is obtained for the maximum torque on wheels. This all is achieved by the use of many clutches controlled by the torque converter. Now shifting to the 2nd gear here large sun gear get locked and planet gear starts revolving around the sun and about its axis also and gear ratio gets reduced. In 3rd gear planetary gears get locked about its axis that is there does not revolve about its axis and gear ratio is further reduced to 1. Now for the 4th gear planet gears serves as power input and the large sun gear is locked and hence gear ratio is further reduced. And last but not the least for reverse gear it is same as first gear but instead of small sun gear here large sun gear serves as input for power.
Comparison with manual Transmission
Comparison with manual Transmission
- It is more compact in size and requires less maintenance.
- Easier to learn and use by an inexperienced driver.
- Automatic Transmission provides a great advantage on slope hill climb because it intelligently selects the gear ratio automatically.
- They are generally less efficient and main causes of this is losses in the torque converter by moving fluid.