Vehicle stepless transmission control device

A control device for a continuously variable transmission of a vehicle, the continuously variable transmission including a primary pulley connected to an output shaft side of a power plant, a secondary pulley connected to a driving wheel side, a circular belt member wound around the pulleys, and an oil pump arranged to be driven by the power plant, and to supply a hydraulic fluid for clamping the belt member to the pulleys, the control device comprising:

• a shift control section configured to control a hydraulic pressure of the hydraulic fluid supplied to the pulleys in accordance with a traveling state of the vehicle, to control clamping forces of the pulleys with respect to the circular belt member, and thereby to control a transmission gear ratio of the continuously variable transmission;
• a road surface judging section configured to judge whether a state of a road surface on which the vehicle travels is a smooth road or a rough road;
• and
• a rotation speed control section configured to control a rotation speed of the primary pulley,
• when the road surface judging section judges the rough road, the shift control section being configured to perform a rough road corresponding control to increase the hydraulic pressure supplied to the secondary pulley to a value larger than the hydraulic pressure when the road surface judging section judges the smooth road, and thereby to increase the clamping force of the secondary pulley with respect to the circular belt member, and
• the rotation speed control section being configured to control the transmission gear ratio at the rough road judgment so that a rotation speed of the primary pulley becomes equal to or greater than a lower limit rotation speed which is previously set.