Just like the manual transmission, an automatic transmission is used in an internal combustion engine. Their major purpose is to convert the engine power to the wheels. An automatic transmission system is also known as an auto, self-shifting transmission, or n-speed automatic. The n represents its number of forwarding gear ratios. This type of transmission is abbreviated as AT.
The internal combustion engine is known for its suitability for running high rotational speed. it provides a range of speed and torque outputs required for vehicular travel. An automatic transmission also gives the same features on a vehicle with such an engine.
What is Automatic Transmission?
The transmission system is a type of motor vehicle transmission that changes the gear ratio automatically. The gear changing occurs as the vehicle moves. Drivers have no business with the gear engagement as it’s manually done in manual transmission.
The hydraulic planetary automatic transmission is the most popular in automobiles. However, larger devices are used for heavy-duty commercial and industrial vehicles as well as equipment.
Some other automated transmissions like the continuously variable transmission (CVT) and automated manual transmissions. They also use the traditional torque converter hydraulic automatic transmission. This is the reason why are classified as types of automatic transmission.
These transmissions also free the drivers from shifting gears manually. It is achieved using the transmissions to change gears.
Below is the complete diagram of automatic transmission:
Automatic Transmission Parts:
Below are the parts of an automatic transmission system:
- Torque converter assembly
- Clutch pack assembly
- Transmission gears
- Torque converter lock-up control solenoid valve assembly
- Shift control solenoid valve assembly
Types of automatic transmission:
Below are the various types of automatic transmissions seen in modern and older vehicles:
Traditional Automatic Transmission:
The traditional automatic transmission is the most common, known as torque converter automatic. It is widely used among all kinds of automated transmission.
A hydraulic fluid coupling or a torque converter is used to perform its operation. These gears changing operation is achieved with a clutch in the manual types of transmission.
Well, ECU (Engine Control Unit) is used to allow smooth and precise engine control of the vehicle. It is directly connected to the transmission mechanism.
Dual-clutch Transmission (DCT):
The dual-clutch transmissions are a combination of automatic and manual transmissions. A torque converter is eliminated but two separate shafts with clutches are used for changing gears.
One shaft is for odd-numbered gears while the other is for the even-numbered. Engaging higher and lower gears can be so smooth but get noisy and rough shifting if wear occurs.
In the dual-clutch transmission, drivers do not need to change gearbox fluid. The clutches are dry and wear out their fractional quality eventually.
The automated-manual types are also known as semi-automatic transmission. It works with a clutch and gear configuration. However, it makes use of sensors, actuators, and processors.
Vehicles with such transmission are known as jerky engine performance. It runs low speeds at hard acceleration, but it’s highly economical in terms of fuel mileage.
Continuously Variable Transmission (CVT):
The CVT types of transmission use belts or pulleys instead of traditional steel gears. Seamless gear shifting is obtained due to the engine speed or RPM. Maximum efficiency and continuous acceleration are accurate in this transmission. But the engine can be so noisy.
The Tiptronic transmission is used on high-performance and sports vehicles. It is also called “manumatic”. This transmission was pioneered by Porsche in the 90s.
It works similarly to a manual gearbox but it uses a torque converter instead of a clutch pedal. This transmission gives a chance for automatic shifting of the gears and drivers can override the automatic mode manual selection of gears.
Tiptronic transmissions are designed with a built-in safety device that prevents the gearbox from damaging. It is achieved with over-revving when downshifting.
Direct Shift Gearbox (DSG):
A direct-shift gearbox is similar to the dual-clutch in setup. It also uses two clutches which disengage alternately in changing gears.
Faster shifting and seamless acceleration are obtained with this transmission. Its modern version offers fuel efficiency that exceeds manual gearboxes.
Unlike the DCT, direct shift gearboxes are wet transmissions. Fluids are regularly changed which must lead to vehicle service or maintenance.
How Automatic Transmission Works
In the working automatic transmission system, the same process occurs just as the manual transmission but it happens backdoor and automatically. The clutch is eliminated in this situation and the transmission relies on the torque converter for the desired speed gears.
When the engine is spinning slowly, very little torque is transmitted through a fluid and turbine inside the torque converter. And when the engine is spinning quickly, all of the engine’s torque is transferred to the transmission. The torque converter is the reason why cars with automatic transmissions move slowly forward when idling and in the drive. A small amount of the engine’s torque is being supplied to the transmission’s input shaft.
As the torque converter is handling the connection of the transmission’s input from the engine. the gears inside the transmission are engaged without the driver’s direct instruction. The transmission uses a single concentric shaft with a set of gears inside and around each other in a planetary arrangement including a sun gear. A planet carrier holds multiple-planet gears and ring gears.
The planetary gear set functions by changing the rate of input to output gear speeds through the engagement of one gear to another. The range of available ratios depends on which is engaged to which. There is a complete hydraulic system or control system that engaged the set of planetary gears at a given time. This hydraulic control system is controlled by an electronic control unit programmed.
The gear sets are connected to the engine’s input by a series of internal clutches, which are controlled by the computer and hydraulic system. It helps the engine to determine the gear ratio that will be output through the output shaft to the drive shaft of the wheel.
That’s it for this article that contains definitions, types, parts, and how automatic transmission works. I hope you enjoyed the reading, if so, kindly comment, share, and recommend this site to other technical students. Thanks!