Getting to know the types of Automatic Gearbox
Get to know the types of automatic gearbox
A gearbox is used in every car in order to transfer mechanical power and coordinate the torque and rotation speed from the power generation source to the consumer. These gearboxes are divided into two main categories, manual and automatic.
The main advantage of automatic gearbox, which has caused the increasing attention of customers and car manufacturers to the production and use of cars with automatic gearboxes, is reducing the driver’s duties while driving and, as a result, increasing the peace and comfort of driving.
Automatic gearbox used in passenger cars are divided into four categories. They are generally divided as follows:
- AMT Gearbox
- CVT Gearbox
- Solar automatic transmission (AT)
- Double clutch gearbox (DCT)
In the following, each of these types of gearbox will be examined separately in the act group.
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1- AMT Gearbox (Automated Manual Transmission)
These types of gearbox actually bring the convenience of using automatic gearbox to the driver, especially in city traffic, while they do not have the complexity and high cost of automatic gearbox.
In fact, this type of power transmission systems are manual gearboxes in which the act of clutching and changing gear is done by an electronic and mechanical set.
The most important advantage of this type of gearboxes is their cheaper and simpler structure compared to other types of automatic gearbox.
Also, because most of its parts are in common with manual gearboxes, they have lower repair costs than other automatic gearboxes.
But these types of gearbox have an unfavorable performance due to very high slippage during gear shifting and are in a much lower category than other automatic gearbox in terms of customer satisfaction.
Figure 1 shows an example of an AMT gearbox. These types of gearbox are mostly used in cheap cars. Qazvin Motor Company (NMI) is manufacturing and producing AMT gearbox for Rana 6-speed car under the brand name AMT6, which is in the final stages of construction and validation.
The available examples of cars with this type of gearbox in Iran are semi-automatic cars Brilliance H220 and MVM 110.
Also read: Specialized webinar “New generation of automatic car gearbox“
Figure 1: AMT gearbox
2- CVT Gearbox (Continuously Variable Transmission)
CVT, shortened to Continuous Variable Transmission, means variable ratio gearbox, these gearboxes are also known by other names such as single speed gearbox.
This type of gearbox was first used by Nissan and was gradually welcomed by other car manufacturers. In continuous power transmission systems, it is possible to change the gear ratio without using engaged gears.
In the most common type of these gearboxes, power is transmitted by two conical pulleys and a metal or polymer belt that connects the pulleys.
Figure 2 It shows an example of this type of gearbox. The most important advantage of this type of gearbox is the continuous gear change.
Therefore, at the moment of gear change, the car experiences less shaking and drop in speed.
One of the disadvantages of this type of gearbox is the impossibility of overloading them, which sometimes causes cars with this gearbox to not perform well on steep road slopes.
This type of gearbox is used in cars such as Haima S5, MVM 550, Jack S3, Nissan Juke and Nissan Tiana, which are not suitable for Iran due to the geography of Iran.
Figure 2: Belt and belt continuous power transmission system
3- Solar planetary gearbox (AT)
Planetary automatic gearbox are the most common types of automatic gearbox in cars. In these gearboxes, power is transmitted through a set of solar gears. Their automatic clutch system is hydraulic (torque converter) and has a control system.
The AL4 gearbox used in 206, 207, SDV9 and Pars Automatic cars, as well as the gearbox of Suzuki Vitara, HC Cross and Haima S7 cars are considered to be of this type.
4- Double clutch gearbox (DCT)
The latest type of gearbox used in cars are double-clutch gearbox, which are called DCT for short. This type of gearbox was first used by Porsche in sports cars and was gradually welcomed by other car manufacturers.
The dual-clutch power transmission system has two concentric input shafts, each of which has an independent clutch. Each of the clutches is engaged with one of the input shafts (orange and purple shafts in Figure 3).
The larger clutch is connected to the odd gears and the smaller clutch is connected to the even gears and they operate separately and at any moment it connects the engine to the wheels according to the desired gear through one of the input shafts.
This feature makes gear changing faster. The average gear change is about 8 milliseconds, which is faster than any other type of gearbox. This advantage reduces the torque disturbance, noticeable shaking of the car and the amount of torque loss during gear shifting.
Double-clutch gearbox have higher prices than normal examples; Because they have both higher technology and more parts.
The number of more parts makes their repair more expensive than normal models, and on the other hand, because there are more parts in them, they weigh more. This type of gearbox is used in cars such as Talisman, Renault Captur, Jack S5, Peugeot 205, Audi R8 and Skoda.
It is necessary to explain that the production and localization of this gearbox is in the roadmap of Iran Khodro until 1402.
In this regard, Jetco has organized a webinar “Getting to know control technologies in the new generation of automatic car gearbox” in cooperation with IRAN KHODRO CO.
Figure 3: Schematic diagram of DCT gearbox
Subscripts:
[1] Automatic Manual Transmission
[2] Continuously Variable Transmission
[3] Automatic Transmission
[4] Dual-Clutch Transmission
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