Patent attributes
Hydraulic control system and method for an automatic transmission. The hydraulic control system includes a hydraulic pressure source, a flow rate control valve having a spool with an orifice and a drain hole, stroke position determining means, and pressure regulator means. The stroke position determining means determines that the spool is displaced from a large spool-stroke position where a communication area of the drain hole is not less than a first predetermined area, to a small spool-stroke position where the communication area is not more than a second predetermined area. The pressure regulator means regulates a hydraulic oil pressure downstream of the orifice and corrects the hydraulic oil pressure downstream of the orifice by adding a predetermined correction amount for a first predetermined time when the stroke position determining means determines that the spool is displaced from the large stroke position to the small stroke position.
