Belt type continuously variable transmission and control method thereof

A control method for a belt type continuously variable transmission which includes a continuously variable shift mechanism having a primary pulley and a secondary pulley, respective pulley widths of which can be modified, and a belt wound around the respective pulleys, which varies a shift ratio by varying the pulley width in order to vary a contact radius between the respective pulleys and the belt, comprising:

• calculating a pulley thrust which is used to bias the respective pulleys in a direction for reducing the pulley width so as to include a predetermined margin;
• controlling an oil pressure supplied to each of the pulleys on the basis of the calculated pulley thrust;
• and
• determining whether or not an upshift, during which the speed ratio is reduced, is underway,
• wherein the predetermined margin is set to be smaller when an upshift is determined to be underway than when an upshift is determined not to be underway.

A belt type continuously variable transmission comprising:

• a continuously variable shift mechanism having a primary pulley and a secondary pulley, respective pulley widths of which can be modified, and a belt wound around the respective pulleys, which varies a shift ratio by varying the pulley width in order to vary a contact radius between the respective pulleys and the belt;
• pulley thrust calculation means for calculating a pulley thrust, which is used to bias the respective pulleys in a direction for reducing the pulley width, so as to include a predetermined margin;
• hydraulic control means for controlling an oil pressure supplied to each of the pulleys on the basis of the calculated pulley thrust;
• and
• upshift determination means for determining whether or not an upshift, during which the speed ratio is reduced, is underway,
• wherein the pulley thrust calculation means sets the predetermined margin to be smaller when an upshift is determined to be underway than when an upshift is determined not to be underway.