Hydraulic servo regulating systems in an automatic transmission

Claim 1

In an automatic transmission of a vehicle having a transmission unit through which power is transmitted in a respective one of power transmitting paths defined therethrough, frictional engaging means operatively connected to the transmission unit for selecting the power transmitting path through which power is transmitted in the transmission unit, hydraulic servos operatively connected to the frictional engaging means for operating or releasing or for engaging or disengaging the frictional engaging means, accumulators operatively hydraulically connected to the hydraulic servos, and a plurality of shift valves operatively hydraulically connected to the hydraulic servos and a source of line pressure and which shift valves are movable between respective positions at which the line pressure is supplied toward the servos and respective positions at which the supply of line pressure is interrupted, a hydraulic servo regulating system comprising: a regulator valve operatively connected to one of the hydraulic servos, one of the accumulators and one of the shift valves, said regulator valve having an application port in hydraulic communication with said one of the shift valves, a regulating port, a spool interposed between said application port and said regulating port and movable between a position at which said ports are open to one another and a position at which said ports are closed to each other, a first feedback port open to one end of said spool and through which feedback pressure passes to act on said spool at said one end thereof, a second feedback port open to another end of said spool and through which feedback pressure passes to act on said spool at said another end thereof, a spring means connected to said spool for exerting an urging force on said spool at said another end thereof, and a drain port openable and closable to said regulating port; the system defining a first oil passage placing said regulating port in hydraulic communication with said one of said hydraulic servos, a second oil passage open to said first oil passage and placing said regulating port in hydraulic communication with said one of said accumulators, a third oil passage open to said first oil passage and placing said regulating port in hydraulic communication with said first feedback port, a fourth oil passage extending between and open to said second oil passage and said first oil passage, and a branch oil passage open to said second oil passage and placing said regulating port in hydraulic communication with said second feedback port; a first orifice disposed in said second oil passage; a second orifice disposed in said third oil passage; and a check valve disposed in said fourth oil passage and allowing oil to flow in said fourth oil passage from said second oil passage toward said first oil passage.