Overview of the basic composition and working proc

2022-08-08
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Overview of the basic composition and working process of automatic transmission

I. basic composition of automatic transmission

there are many brands and models of automatic transmission, and the external shape and internal structure are also different, but their composition is basically the same, which is a combination of hydraulic torque converter and gear automatic transmission. Common components include hydraulic torque converter, planetary gear mechanism, clutch that will not change for several decades, brake, oil pump, filter, pipeline, control valve body, speed regulator, etc. according to the functions of these components, they can be divided into five parts: hydraulic torque converter, variable speed gear mechanism, oil supply system, automatic shift control system and shift control mechanism

1. Hydraulic torque converter

the hydraulic torque converter is located at the front end of the automatic transmission and is installed on the flywheel of the engine. Its function is similar to that of the clutch in vehicles with manual transmission. It uses the change of kinetic energy in the process of oil circulation to transmit the power of the engine to the input shaft of the automatic transmission, and can automatically and steplessly change the transmission ratio and torque ratio within a certain range according to the change of vehicle driving resistance. It has a certain function of reducing speed and increasing torque

2. Variable speed gear mechanism

the types of variable speed gear mechanism in automatic transmission include ordinary gear type and planetary gear type. Ordinary gear transmission is adopted. Due to its large size and small maximum transmission ratio, only a few models adopt it. At present, the gear transmission in most car automatic transmissions adopts planetary gear type

the variable speed gear mechanism mainly includes planetary gear mechanism and shift actuator

planetary gear mechanism is one of the important components of automatic transmission, which is mainly composed of sun gear (also known as center gear), inner ring gear, planet carrier, planet gear and other components. Planetary gear mechanism is a mechanism that realizes speed change. The change of speed ratio is realized by using different components as driving parts and limiting the movement of different components. In the process of changing the speed ratio, the whole planetary gear set still moves, and the power transmission is not interrupted, so the power shift is realized

The shift actuator is mainly used to change the driving element in the planetary gear or limit the movement of a certain element, and change the direction and speed ratio of power transmission. It is mainly composed of multi plate clutch, brake and one-way overrunning clutch. The function of clutch is to transmit power to a component of planetary gear mechanism to make it become the driving part. The function of the brake is to hold a component in the planetary gear mechanism and make it immobile. The one-way overrunning clutch is also one of the shift elements of the planetary gear transmission. Its function is basically the same as that of the multi plate clutch and brake. It is also used to fix or connect some basic elements such as sun gear, planet carrier and ring gear in several planetary rows, so that the planetary gear transmission can form gears with different transmission ratios

3. Oil supply system

the oil supply system of automatic transmission is mainly composed of oil pump, experimental force display under the oil tank, filter, pressure regulating valve and pipeline. Oil pump is one of the most important assemblies of automatic transmission. It is usually installed behind the torque converter and driven by the shaft sleeve at the rear of the torque converter housing. When the engine is running, whether the car is running or not, the oil pump is running to provide hydraulic oil with a certain oil pressure for the torque converter, shift actuator and automatic shift control system in the automatic transmission. The adjustment of oil pressure is realized by the pressure regulating valve

4. Automatic shift control system

the automatic shift control system can automatically connect or cut off the oil supply circuit of some shift clutches and brakes according to the set shift law according to the load of the engine (throttle opening) and the driving speed of the vehicle, so as to combine or separate the clutches, brake or release the brakes, so as to change the transmission of the gear transmission, so as to realize automatic shift

the automatic shift control system of automatic transmission includes hydraulic control and electro-hydraulic (Electronic) control

the hydraulic control system is composed of valve body, various control valves and oil circuits. The valves and oil circuits are set in one plate, which is called valve body assembly. Different models of automatic transmission valve body assembly have different installation positions, some are installed on the upper part, some on the side, and the longitudinal automatic transmission is generally installed on the lower part

in the hydraulic control system, adding solenoid valves to control some hydraulic oil circuits becomes an electrical shift control system. If these solenoid valves are controlled by an electronic computer, they become an electronically controlled shift system

5. Shift control mechanism

the shift control mechanism of automatic transmission includes the control mechanism of manual selection valve and throttle valve. The driver changes the position of the manual valve in the valve plate through the joystick of the automatic transmission. The control system uses the hydraulic automatic control principle or the electronic automatic control principle to control the work of the shift actuator in the gear transmission according to a certain law according to the position of the manual valve, the throttle opening, the vehicle speed, the state of the control switch and other factors, so as to realize automatic shift

second, the working process of the automatic transmission

they found that lignin from hardwood has the best thermal stability. The reason why the automatic transmission can realize automatic shift is that the position where the driver steps on the accelerator or the vacuum degree of the engine intake manifold and the driving speed of the car can command the operation of the automatic shift system, The different working states of each control valve in the automatic shift system will control the separation and combination of the clutch and the braking and release of the brake in the variable speed gear unit, and change the power transmission route of the variable speed gear unit, The shift control mode of the traditional hydraulic automatic transmission is to mechanically convert the speed and throttle opening signals into control oil pressure, and add the oil pressure to both ends of the shift valve to control the position of the shift valve, so as to change the oil circuit of the shift actuator (clutch and brake). In this way, the working hydraulic oil enters the corresponding actuating elements to engage or disengage the clutch, brake or release, and control the upshift or downshift of the planetary gear transmission, so as to realize automatic transmission

electronic hydraulic automatic transmission is formed by adding an electronic control system on the basis of hydraulic automatic transmission. It monitors the running state of the car and engine through sensors and switches, accepts the instructions of the driver, and converts the obtained information into electrical signals and inputs them into electricity? The shift valve of the hydraulic control device enables it to open or close the oil circuit to the shift clutch and brake, so as to control the shift time and gear change, so as to realize automatic transmission. (end)

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