Main Regulator Valve
The main regulator valve maintains constant hydraulic pressure from the ATF pump to the hydraulic control system, while also providing fluid to the torque converter and the lubrication system. Fluid from ATF pump flows through the 1 cavity and the 1' cavity of the main regulator valve. Then the fluid entered in the 1' cavity pushes the main regulator valve to the spring side, this movement uncovers the fluid ports to the torque converter and the lubrication system on the main regulator valve. The fluid flows out to the torque converter and the lubrication system, then the main regulator valve returns under spring force when the pressure in the 1' cavity of the main regulator valve is lowered below that in the 1 cavity, which covers the fluid ports to the torque converter and the lubrication system. According to the level of the hydraulic pressure through the V cavity, the position of the main regulator valve changes, and the amount of fluid from the 1 cavity through the torque converter changes. This operation is continued maintaining the line pressure.
Line Pressure Control during Low Loading
Both in D or S under low engine load condition after warming up the engine and in all ranges (P, R, N, D, or S) under the low ATF temperature condition, the PCM operates line pressure solenoid valve A, and switches the line pressure to a pressure that is lower than normal. This operation can reduce the friction in the transmission.
The PCM turns line pressure solenoid valve A ON, and applies the hydraulic pressure to the PLA' cavity on the main regulator valve. When hydraulic pressure is applied to the PLA' cavity, the main regulator valve is pushed to the spring side. This operation reduces the drain port of the main regulator valve, and causes the line pressure to be lower than normal.