Control system for a four-speed automatic transmission

A control system for an automatic transmission having four forward speeds and a reverse speed, said automatic transmission including a hydrokinetic torque converter having an integral torsion damper, said automatic transmission including a planetary gear train controlled by three clutches and two brakes, said clutches and brakes each being activated by hydraulic means, said control system comprising:

• a hydraulic distributor including means for selectively distributing hydraulic fluid to said hydraulic means of said clutches and brakes;
• four solenoid valves operatively connected to said means for selectively distributing for actuating said means for selectively distributing;
• and
• control means sensitive to vehicle operation data for controlling said four solenoid valves, wherein said means for selectively distributing comprises:
• means for distributing said hydraulic fluid at one of two flow rates for any line pressure by actuation of at least some of said four solenoid valves,
• three sequence valves each being connectable to a source of hydraulic fluid and having a movable spool connected to a respective one of three of said solenoid valves for distributing said hydraulic fluid, and
• a progressiveness valve connectable to said source of hydraulic fluid and having a movable spool connected to a fourth of said solenoid valves for distributing said hydraulic fluid,
• wherein said means for distributing at one of two rates comprises a feed duct for said hydraulic means for said clutches and brakes with a large passage section and including said progressiveness valve, in parallel with a feed duct for said hydraulic means for said clutches and brakes with a small passage section, whereby said hydraulic fluid can be supplied to said hydraulic means at a reduced flow rate by using said progressiveness valve to close said feed duct having said large passage section.