Patent ID: 6159124
Filing Date: 2000-12-12
Classification: F16H,Y10S

Abstract:
A hydraulic control system for an automatic transmission including a planetary gear system having a plurality of clutch elements engagable to alter the torque ratio of the transmission, said hydraulic control system comprising:a pressurized fluid source;a manual valve selectively movable between a plurality of positions and communicating with said pressurized fluid source, said plurality of positions including reverse, drive and second;a first fluid passage communicating with one of said plurality of clutch elements and said manual valve, said first fluid passage including a normally open solenoid valve;a second fluid passage communicating with a second one of said plurality of clutch elements and said manual valve, said second fluid passage including a normally closed solenoid valve;wherein said manual valve continuously communicates with said first fluid passage while manual valve porting is switched between said drive position and said second position; andfurther comprising a third fluid passage communicating with said second one of said plurality of clutch elements, said third fluid passage including a second normally open solenoid valve which provides a communication to said second clutch element through a ball check valve when said manual valve is in a predetermined position and said second normally open solenoid valve is de-energized.