Patent ID: 6800044
Filing Date: 2004-10-05
Classification: F16H

Abstract:
A speed change control apparatus for a continuously variable transmission for a vehicle having, a driving wheel provided under said vehicle for driving thereof by a driving power through a crankshaft from an engine, a primary shaft mechanically and coaxially connected to said crankshaft for receiving said driving power, a primary pulley provided on said primary shaft for axially changing a width, a secondary shaft provided in parallel with said primary shaft, a secondary pulley provided on said secondary shaft for transmitting said power through a belt wound on both of said pulleys and for changing each rotating speed depending on driving conditions of said vehicle, a primary cylinder formed on an outer periphery of one side of said primary pulley for including a primary oil chamber, a secondary cylinder formed on said outer periphery of one side of said secondary pulley for including a secondary oil chamber, an oil pump mounted on said vehicle for supplying an actuating fluid to said primary and secondary oil chambers via a pressure line, said speed change control apparatus comprising:a line pressure control valve interposed in said pressure line between said oil pump and said primary oil chamber for adjusting an oil pressure therebetween to a line pressure; a primary pressure control valve interposed in said pressure line between said line pressure control valve and said primary oil chamber for adjusting an oil pressure therebetween to a primary pressure; and a switchover valve interposed in said pressure line between said oil pump and said secondary cylinder for switching to supply said actuating fluid of said line pressure to said secondary oil chamber and to supply said actuating fluid of said primary pressure and of said line pressure as much as required for shifting to said primary oil chamber when said vehicle runs at a low speed and for switching to supply said actuating fluid of said line pressure to said primary pressure oil chamber and to supply said actuating fluid of said primary pressure and of said line pressure as much as required for shifting to said secondary oil chamber when said vehicle runs at a high speed so as to effectively decrease an inertia capacity of said primary cylinder by decreasing a diameter of said a primary cylinder thereby to improve responsiveness of a speed change.