Shift control system for belt-type continuously variable transmission

A shift control system for a belt-type continuously variable transmission which comprises a variable width drive pulley, a variable width driven pulley, a V belt, a drive-side actuator and a driven-side actuator, said V belt being disposed around said drive and driven pulleys, said drive-side actuator generating an axial thrust to said drive pulley, and said driven-side actuator generating an axial thrust to said driven pulley, wherein said shift control system controls the drive axial thrust generated by said drive-side actuator and the driven axial thrust generated by said driven-side actuator to vary the widths of said drive and driven pulleys for achieving a shift to a target speed change ratio;

• said shift control system comprising:
• contact-circle enlarging pulley determination means for determining which pulley, of said drive pulley or said driven pulley, is to be a contact-circle enlarging pulley whose diameter of a contact circle around which said V belt is disposed is enlarged when the widths are varied in shift control;
• and
• additional thrust calculation means for calculating a shifting additional thrust which is added to the axial thrust for said contact-circle enlarging pulley to achieve said shift to said target speed change ratio.