汽车自动变速器与驱动桥全套PPT电子课件.ppt

A shift solenoid is either on or off, and it strokes once to make an upshift or downshift. Some 4-speed transmissions use two shift solenoids that are both on, both off, or one open at one time. One modern 6-speed transmission uses 8 solenoids: 6 shift solenoids, an EPC solenoid, and torque converter clutch (TCC) solenoid. Animations: Shift Solenoid Operation 1 and 2 * Both shift solenoids are on so both shift valves are down-shifted. Shift valve pressure is exhausted at the solenoids. Shift Solenoids Shift Valves * No. 2: On No. 1: Off Turning Solenoid No. 1 off causes a pressure increase that moves the 1-2 shift valve to upshift. This applies the intermediate band to make the shift to 2nd gear. 1-2 Shift Valve * The amount of output force is determined by the area of the output piston and the amount of fluid pressure. 100 psi pushing on 2 square inches generates a force of 200 pounds. Animation: Pressure at Work * Fluid force equals Pressure times Piston Area. Piston Area equals ? (3.1416) times Piston Diameter. F = P X A A = ? D Area Diameter * This simple system contains a sump to store the fluid, a filter to clean the fluid, a pump to move the fluid and create pressure, a pressure regulator valve to control fluid pressure, a control valve to control fluid flow, and an actuator to do the work. Animation: Simple Hydraulic Shifts * When pump pressure gets stronger than the spring, the pressure regulator valve (green) will move upward. Valve movement will open the passage to the torque converter. Further movement from higher pressure will move the valve to allow excess pressure to return to the pump inlet. Animation: Pressure Regulator Valve * Automatic transmissions use spool valves to control the fluid flows. This manual valve is positioned by the shift lever. It determines the operating sequence that is desired by the driver. Animation: Manual Valve: Park * Spool Valves resemble a spool for thread. The valve lands fit closely inside of the valve bore. When t