The transmission is a mechanism used to change the speed and torque from the engine. It can change the transmission ratio between the output shaft and the input shaft in a fixed or stepped manner, also known as a gearbox. The transmission is composed of a variable speed transmission mechanism and a steering mechanism, and some cars also have a power output mechanism. Most of the transmission mechanisms are driven by ordinary gears, and some are driven by planetary gears. Ordinary gear transmission transmission mechanism generally uses sliding gears and synchronizers.
1. Divided by the way the transmission ratio changes, the transmission can be divided into three types: stepped, stepless and integrated. (a) Stepped transmission: There are several alternative fixed transmission ratios, geared. It can be divided into two types: ordinary gear transmission with fixed gear axis and planetary gear transmission with partial gear (planetary gear) axis rotation. (b) Continuously variable transmission: The transmission ratio can be continuously changed within a certain range. Common hydraulic, mechanical and electric types are available. (c) Integrated transmission: Composed of a stepped transmission and a continuously variable transmission, its transmission ratio can be infinitely changed within a range of several steps between the maximum and minimum values.
2. Divided by the operation mode, the transmission can be divided into three types: forced operation, automatic operation and semi-automatic operation. (a) Force-operated transmission: The driver directly manipulates the shift lever to shift gears. (b) Automatically operated transmission: Selection of gear ratios and shifting are performed automatically. The driver only needs to operate the accelerator pedal, and the transmission can control the actuators according to the load signal and the speed signal of the engine to realize the shift of gears. (c) Semi-automatic transmission: It can be divided into two types, one is automatic gear shifting in some gears, and manual (forced) gear shifting in some gears; the other is to select gears with buttons in advance and press the clutch When the pedal is released or the accelerator pedal is released, the actuator shifts gears by itself.
Simple transmission has the advantages of high efficiency, simple structure and easy to use, but with few gears and small change range of i (traction and speed range is small), it should only be used by some lathes with few gears. If the range of i is increased, the size of the transmission will be increased, and the shaft span will be increased. In order to increase the number of gears without making the shaft span too large, a component transmission can be used. The so-called component transmission is usually composed of two simple transmissions. Among them, the more gears are called the main transmission and the less are called the auxiliary transmission.
(1) Change the transmission ratio to meet the requirements of traction for different driving conditions, and make the engine work under favorable conditions as much as possible to meet the requirements of possible driving speed. Change the speed of the car and the torque on the drive wheels of the car within a wide range. Due to the different driving conditions of the car, it is required that the car’s driving speed and driving torque can be changed within a wide range. For example, the speed on a highway should reach 100 km / h, while in urban areas, the speed is usually around 50 km / h. When an empty car is driving on a straight road, the driving resistance is very small, and when it goes uphill with a full load, the driving resistance is very large. The characteristic of the automobile engine is that the range of the speed change is small, and the range of the torque change can not meet the actual road conditions.
(2) Realize reverse driving, which is used to meet the needs of the car driving backwards. To achieve reverse driving, the crankshaft of the engine can generally only rotate in one direction, and the automobile sometimes needs to be able to travel backwards. Therefore, the reverse gear set in the gearbox is often used to achieve reverse driving.
(3) Interrupt the power transmission. When the engine is started, idling, the car is shifted or the vehicle needs to stop for power output, the power transmission to the drive wheels is interrupted.
(4) To achieve neutral, when the clutch is engaged, the gearbox may not output power. For example, it can be guaranteed that the driver releases the clutch pedal and leaves the driver’s seat when the engine is not turned off.