Hydraulic pressure-control valve for automatic vehicle transmission

A hydraulic pressure-control valve for controlling a pressure to be supplied to a frictional engaging element in an automatic vehicle transmission, including:

• an hydraulic pressure source;
• a first pressure-regulating valve connected to the hydraulic pressure source through a first passage to input an input hydraulic pressure from the hydraulic pressure source and connected to the frictional engaging element through a second passage;
• valve displacing means for displacing the first-pressure regulating valve at one end in a first direction such that the first pressure-regulating valve outputs an output hydraulic pressure to the frictional engaging element in response to a command input;
• and
• piston connected to the first pressure-regulating valve such that the output hydraulic pressure varies by a first amount per unit of command input in response to the command input according to a first characteristic, while the output hydraulic pressure varies by a second amount, different from the first amount, per unit of command input in response to the command input according to a second characteristic;
• wherein the improvement comprises:
• the valve displacing means determines a pressure-control position of the first pressure-regulating valve which regulates the output hydraulic pressure;
• and
• the first pressure-regulating valve and the piston are connected such that the output hydraulic pressure is applied to the first pressure-regulating valve at an end opposite to the one end and the piston acts to determine the pressure-control position of the first pressure-regulating valve in response to the applied output hydraulic pressure.