Once, when someone saw a CVT gearbox, there was a part called the valve body. The structure inside was like a labyrinth, and it was full of oil. What's the function of this part?
Control of hydraulic mechanical transmission type automatic transmissionHydraulic automatic control system is usually composed of oil supply, manual block selection, parameter adjustment, shift time control, shift quality control and other parts.The oil supply section adjusts the output hydraulic pressure of the oil pump to the required value according to the opening of the throttle valve and the change of the position of the selector rod to form a steady working hydraulic pressure.In the hydraulic controlled hydraulic automatic transmission, parameter adjustment mainly consists of a solar term door pressure regulating valve (referred to as solar term valve) and speed control pressure regulating valve (also called the governor). The throttle pressure regulating valve enables the output hydraulic pressure to reflect the opening of the throttle valve; the speed control regulating valve makes the output hydraulic pressure reflect the speed of the valve.The shift time control part is used for converting the oil circuit leading to each shift actuating mechanism (clutch and brake) so as to realize shift control. The locking signal valve is controlled by an electromagnetic valve so that the locking clutch in the torque converter is joined and separated in a timely manner. The role of shift quality control is to make the shift process more smooth and gentle.
The working principle of planetary gear transmissionAlthough torque converter can transfer and increase the engine torque, but the torque ratio is not large, the speed change range is not wide, it can not meet the needs of the vehicle working conditions. In order to further enlarge the torque, enlarge the range of speed change and improve the adaptability of the automobile, an auxiliary transmission is also installed behind the hydraulic torque converter with a stepped gear transmission. The gear transmission is mostly planetary gear.Planetary gear transmission is composed of planetary gear mechanism and clutch, brake and one-way clutch. Planetary gear bodies are usually composed of multiple planetary rows, and the number of planets is related to the number of gears. The shift actuator of the planetary gear transmission includes a shift clutch, a shift brake and a one-way switch.The shift clutch is a wet multi plate clutch. When the hydraulic pressure causes the piston to press the driving plate and the driven piece, the clutch engages; when the working fluid is discharged from the piston cylinder, the return spring causes the piston to retreat and the clutch is separated.The brake shift usually has two forms: one is the wet multi disc brake, and the structure of clutch is basically the same, the difference is used to connect the brake rotating parts and the transmission housing, the rotating parts can not rotate. Another form of the shift brake is the outer beam type belt brake. The one-way clutch of the planetary gear transmission is the same as the one-way clutch in the hydraulic torque converter.
The speed at which the fluid flows out of the turbine V can be seen as the rate at which the work fluid flows out relative to the surface of the turbine blade, and is combined with a rotational velocity U of the turbine. When the turbine speed is relatively small, the working fluid flowing out of the turbine is backward, and the working fluid impacts the front of the guide wheel blade. Because the guide wheel is limited by a one-way clutch, it can not rotate backward, so the guide vane moves the working fluid backward to guide the impeller of the pump wheel to promote the rotation of the pump wheel, thereby increasing the torque acting on the turbine.As the turbine speed increases, the rate of u increases as the speed V of the Omega and u begins to point to the back of the guide vanes. The torque converter reaches the critical point. When the turbine speed increases further, the working fluid will impact the back of the guide wheel blade. Because the unidirectional clutch allows the guide wheel to rotate forward with the pump wheel, the guide wheel rotates freely along the rotation direction of the pump wheel under the driving of the working fluid, and the working fluid flows back to the pump wheel smoothly. When the working fluid outflow from the turbine guide vane outlet coincides with the same direction, the torque converter is not produced by twisting effect (the torque converter condition called hydraulic coupling condition).
Working principle of hydraulic torque converterAt present, the single stage, double phase and three element locking type hydraulic torque converter is widely used in the car, consisting of pump wheels, turbine and guide wheel. The pump wheels and turbines are in pots. With the pump wheel torque converter shell is connected as a whole, active element; turbine suspension in the torque converter, connected by spline and the output shaft is a driven element; guide wheel is suspended between the pump and turbine wheel through a one-way clutch and a guide wheel shaft sleeve is fixed on the transmission housing.When starting the engine, the crankshaft drives the pump wheel rotation, because of the centrifugal force generated by the rotation of the working liquid pump wheel between the leaves along the blade from the inner edge to the margin thrown out; speed of this part of the work fluid has both rotate with the pump wheel park circumferential and axial, rushed to the turbine speed. The working fluid impacts the turbine blades and pushes the turbine to rotate in the same direction as the pump wheels.
The body of the general gearbox is used for high and low conversion. When the speed reaches a certain gear speed, the hydraulic oil pushes the valve body to change the gear to the gear automatically.The automatic transmission can automatically change the transmission ratio according to the engine load and speed, so as to make the vehicle obtain good power and fuel economy, and reduce engine exhaust pollution. The automatic transmission is easy to operate, and can greatly improve the safety and reliability of the vehicle when the vehicle is crowded. Electronic control automatic transmission is usually composed of hydraulic torque converter, planetary gear transmission system, shift actuator, hydraulic control system, electronic control system of five parts.
