P file, n file, d file, r file. What do you mean?

P is the parking gear, N seems to be neutral, D is the forward gear and R is the reverse gear. These four gears are available in every automatic car. There are three kinds of automatic gearboxes commonly used in automobiles, namely at gearboxes, cvt gearboxes and dual clutch gearboxes. Dual clutch gearbox is a product developed on the basis of manual gearbox. This gearbox is similar in structure to a manual gearbox. The dual clutch gearbox only has one more clutch and one shift control mechanism than the manual gearbox. One clutch of the dual clutch gearbox is used to control odd gears, and the other clutch is used to control even gears. Dual clutch gearbox has fast shifting speed and high transmission efficiency. Cvt gearbox is an automatic gearbox with simple structure. This gearbox has only two helical gears and a steel plate chain. The steel chain of cvt can move on the helical gear, so that the transmission can change speed and twist. Cvt has good shift smoothness, reliability and durability. At gearbox is the most mature and widely used automatic gearbox at present. There are many planetary gears in the gearbox. This gearbox relies on planetary gears to change speed and torque. The shift smoothness of at gearbox is better than that of dual clutch gearbox, and the torque it can bear is also higher than that of cvt gearbox.