Patent ID: 7112154
Filing Date: 2006-09-26
Classification: F16H,Y10T

Abstract:
1. A hydraulic control system for an automatic transmission, comprising: a hydraulic pressure source operative to discharge a hydraulic oil amount; a flow rate control valve disposed on a discharge side of the hydraulic pressure source, the flow rate control valve including a displaceable spool formed with an orifice and a drain hole, the drain hole having a communication area which is fluidly communicated with an outside of the flow rate control valve and varied during displacement of the spool, the spool having a large stroke position where the communication area is not less than a first predetermined area, and a small stroke position where the communication area is not more than a second predetermined area, the flow rate control valve being operative to control a flow rate of the hydraulic oil amount passing through the orifice by regulating the hydraulic oil amount drained from the communication area depending on displacement of the spool; stroke position determining means for determining that the spool is displaced from the large stroke position to the small stroke position; and pressure regulator means for regulating a hydraulic oil pressure downstream of the orifice, the pressure regulator means correcting the hydraulic oil pressure downstream of the orifice by adding a predetermined correction amount of hydraulic pressure 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.