What is a transmission

Transmission , also known as gearbox, is a mechanism used to change the speed and torque from the engine. It can change the transmission ratio of the output shaft and input shaft in fixed or step-by-step steps. Speed changer is made up of speed change transmission mechanism and operating mechanism, and some automobiles also have power output mechanism. Most of the transmission mechanisms are driven by ordinary gears, and some are driven by planetary gears. Ordinary gear transmission transmission mechanisms generally use slip gears and synchronizers.

Common Terms for Transmissions

(1) Driving gear and driven gear. The input shaft can be understood as being connected to the clutch and rotating under the drive of the engine, and the gear fixed on the input shaft rotates synchronously with it, which is called the driving gear. This gear is called a driven gear.

(2) Transmission ratio i. The ratio of the number of teeth of the driven gear to the number of teeth of the driving gear is defined as the transmission ratio.

When the relationship between the number of teeth of the driven gear and the number of teeth of the driving gear changes, the transmission ratio i changes. Under the condition of constant engine speed, it will affect the change of the output shaft speed, that is, the change of the wheel speed. A pair of gears meshing with each other, the number of teeth will not change during use, so its transmission ratio is fixed. If several gears with varying numbers of teeth are installed on the input shaft to mesh with corresponding gears with varying numbers of teeth on the output shaft, a set of stepped transmissions with different transmission ratios i can be obtained. Automobile transmission is to realize gear shifting according to this basic principle.

(3) Forward gear, the gear that can make the car move forward. Reverse gear, the gear that can make the car run backwards. In neutral, each gear in the transmission is not in the working position. At this time, after the engine power is input to the input shaft, it is no longer transmitted to the output shaft.

(4) Direct file. The engine power is not transmitted through any gear in the transmission, but the gear directly output through the transmission input shaft and the output shaft directly connected with it is called direct gear. The direct gear ratio is 1.

(5) Overdrive. That is, the speed of the output shaft is higher than the speed of the input shaft.

(6) Number of files. Refers to the number of gears that a stepped gear transmission has. The gears of commonly used gear transmissions are four to five gears, and three-speed transmissions are rare. The more the number of gears, the better the adaptability of the car to the driving conditions and the lower the fuel consumption, but the more complicated the transmission mechanism and the control mechanism, the more difficult the operation and the higher the cost.

(7) Low-grade, high-grade. Among the gear positions of the transmission, the gear with a small number is called a low gear. The gear with a smaller number has a larger transmission ratio, a greater traction force, and a lower speed. For example, the transmission ratio of the first gear is the largest in the forward gear, the vehicle speed is the lowest, and the traction is the largest. The gear with a large number is called a high gear, and the larger the number, the smaller the transmission ratio and the smaller the traction force, but the higher the vehicle speed.

(8) SHIFT. The conversion process of the transmission to complete the transmission ratio is called gear shifting. The gear shifting of the sleeve, the gear shifting is called the gear shifting of the sleeve through the engagement ring gear on the tooth side and the sleeve that are integrated with the gear to mesh (or separate) to realize the conversion of the transmission ratio. Synchronizer shift, utilize synchronizer to shift gears. Not only is the gear change free of bumps and noises on the mating teeth, but the shifting time is also short.

(9) Skipping files. When the car is running, due to the wear and vibration of the engaging teeth, the engaging sleeve is separated from the engaging ring gear and the transmission is in a neutral state.

Classification of transmission

Stepped transmission

The stepped transmission is the most widely used one. It adopts gear transmission and has several fixed value transmission ratios. According to the different types of gear trains, there are two types of shaft-fixed transmissions (ordinary transmissions) and shaft-rotating transmissions (planetary gear transmissions). Transmission ratios for passenger cars and light and medium trucks usually have 3-5 forward gears and one reverse gear, and in compound transmissions for heavy trucks, there are more gears. The so-called number of gears in the transmission refers to the number of forward gears.

CVT

Continuously variable transmission refers to a transmission system that can continuously obtain any transmission ratio within the transmission range. The best match between the drive train and the engine operating conditions can be obtained through continuously variable transmission. Common continuously variable transmissions include hydromechanical continuously variable transmission and metal belt continuously variable transmission (VDT-CVT).

Integrated transmission

The comprehensive transmission refers to a hydromechanical transmission composed of a hydraulic torque converter and a gear-type stepped transmission. Its transmission ratio can be continuously changed within several intermittent ranges between the maximum value and the minimum value. Currently There are many applications.

The function of the transmission

(1) Change the transmission ratio to meet the traction needs of different driving conditions, so that the engine can work under favorable working conditions as much as possible to meet the possible driving speed requirements. Change the speed of the car and the torque on the driving wheels of the car in a large range. Due to the different driving conditions of the vehicle, it is required that the driving speed and driving torque of the vehicle can vary in a wide range. For example, the speed of the vehicle on the highway should be able to reach 100km/h, while in the urban area, the speed of the vehicle is often around 50km/h. When an empty car is driving on a straight road, the driving resistance is very small, but when it is fully loaded uphill, the driving resistance is very large. The characteristics of automobile engines are that the range of speed variation is small, and the range of torque variation cannot meet the needs of actual road conditions.

(2) Reversing driving is realized, which is used to meet the needs of automobiles running backwards. Realize reversing driving automobile, engine crankshaft generally all can only be rotated to one direction, and automobile needs to be able to run backwards sometimes, therefore, often utilize the reverse gear that is provided with in the gearbox to realize automobile reversing driving.

(3) Interrupt power transmission. When the engine is started, idling, the car shifts gears or needs to be stopped for power output, the power transmission to the driving wheels is interrupted.

(4) Realize the neutral gear, when the clutch is engaged, the gearbox can not output power. For example, it can be guaranteed that the driver releases the clutch pedal to leave the driver's seat without shutting down the engine.

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