System for controlling a continuously variable transmission of a motor vehicle

In a system for controlling a solenoid operated control valve in a continuously variable transmission to transmit power of an internal combustion engine to driving wheels of a motor vehicle, said transmission having a drive pulley including a hydraulically shiftable disc and a first hydraulic cylinder for shifting said disc, a driven pulley including a hydraulically shiftable disc and a second hydraulic cylinder for operating said disc of said driven pulley, a belt engaged with both pulleys, said control system having a solenoid for operating said solenoid operated control valve, and a control unit for controlling dither exciting current fed to said solenoid and for producing a basic exciting current signal, an improvement of the system which comprises:

• dither means responsive to said basic exciting current signal for providing a dither and for generating a dither signal;
• calculating means responsive to said dither signal for adding said dither to said basic exciting current and for producing said dither exciting current signal;
• integration means responsive to said dither exciting current signal for integrating deviation of said dither exciting current from said basic exciting current and for producing a integral signal;
• correction means responsive to said integral signal for producing a correction value dependent on said integrals and for generating a correction signal;
• said dither means responsive to said correction signal for correcting said dither and for producing a corrected dither signal;
• and
• said calculating means responsive to said corrected dither signal for producing a corrected dither exciting current for exciting said solenoid so as to accurately control valve without fluctuation.