Primary Regulator Valve
This valve controls the hydraulic pressure (line pressure) generated by the oil pump by using the throttle pressure, the line pressure when the gear is shifted to the "R" range and the spring force.
The hydraulic pressure generated by the oil pump (line pressure) is applied to (1) and (3) trying to lower the valve. On the other hand, the throttle pressure applied to (4) tries to raise the valve together with the spring force.
In this way, as the valve moves up and down, the line pressure is released through (2) so that it is adjusted according to the state of the throttle pressure. From (6) and (7), the hydraulic pressure is sent to the secondary regulator valve. When the gear is shifted to the "R" range, as the hydraulic pressure is also applied to (5), increasing the force to raise the valve the hydraulic pressure (line pressure) is adjusted to a higher value than in any other range.