Manual, automatic, manual-automatic integrated transmission... The wide variety of transmissions confuse many car buyers, but they all have only one mission: to change speed and torque, that is, to increase speed while reducing torque or decrease speed while increasing torque. In general, there are several classifications as follows:
1. Manual Transmission (MT): A manual transmission contains several sets of gears. The driver manually selects which set of gears to use according to different driving conditions through the transmission control mechanism, thus changing the gear ratio to achieve the purpose of changing speed and torque. Since there exists a "synchronization" issue when shifting gears, many modern transmissions now use synchronizers to improve the smoothness of gear changes.
Characteristics: Direct gear changes provide more driving pleasure for the driver. Purely mechanical transmission, with little power loss, has better fuel economy. Simple structure of manual transmission, less maintenance costs.
2. Automatic Transmission (AT): An automatic transmission uses planetary gear sets to change speed. It can automatically shift gears according to the degree of the accelerator pedal and the speed changes, and the driver only needs to control the acceleration pedal to control the vehicle speed, reducing the difficulty of driving. Generally speaking, common types of automatic transmissions used in cars include hydraulic automatic transmission, hydrodynamic automatic transmission, electric automatic transmission, etc. Among them, the most common one is the hydraulic automatic transmission composed of a torque converter and a gear-type stepped transmission, whose gear ratio can make stepless changes within several discontinuous ranges between the maximum and minimum values. Due to the power transmission loss of the torque converter, the transmission efficiency of the automatic transmission is usually only 85%.
Characteristics: Smooth power transmission, natural gear change transition. However, complex structure, higher maintenance costs, some power loss, and reduced fuel economy.
3. Continuously Variable Transmission (CVT): A continuously variable transmission consists of two sets of variable-speed pulleys and a drive belt. Therefore, it is simpler in structure and smaller in size than traditional automatic transmissions. Besides, it can freely change the gear ratio, thereby achieving continuous stepless speed change throughout the process, making the car speed change smoothly without the "jerk" feeling when traditional transmissions shift gears.
Characteristics: Achieves uninterrupted power output, and there is no impact vibration when switching gears like in stepped transmissions, with better power performance and economic performance compared to traditional stepped automatic transmissions.
4. Manual/Automatic Transmission: This was first introduced by Porsche on the 911 model. It allows high-performance sports cars to be free from the constraints of traditional automatic transmissions, allowing drivers to enjoy the fun of manual gear changes. This type of car has "+" and "-" selection gears on its gearshift. When in D gear, you can freely change down (-) or up (+) gears, just like a manual transmission. Drivers can force downshift and decelerate before entering a corner like a manual transmission, and accelerate out of the corner in low-middle gear. Now, "+" and "-" gear shift buttons have been added to the steering wheel of automatic cars, allowing drivers to shift gears without taking their hands off the steering wheel.