Patent ID: 6135915
Filing Date: 2000-10-24
Classification: F16H,Y10T

Abstract:
A method of controlling a transmission ratio in a belt-type stepless transmission device wherein engine output is transmitted to vehicle wheels by varying the transmission ratio in a stepless fashion by setting axial thrusts of a drive pulley and a driven pulley, the method comprising the following steps:setting a target transmission ration and a target rate of change of transmission ratio based on a vehicle speed and a degree of accelerator opening;determining a driven pulley necessary axial thrust and a drive pulley necessary axial thrust necessary to effect power transmission without causing belt slippage based on a transmission device input torque and a transmission ration;setting said driven pulley necessary axial thrust as a driven pulley target axial thrust, setting the drive pulley necessary axial thrust as a drive pulley target axial thrust in order to change the transmission ratio to said target transmission ratio with said target rate of change of transmission ratio using said driven pulley target axial thrust;comparing said drive pulley target axial thrust and said drive pulley necessary axial;performing transmission ratio control using said drive pulley target axial thrust and said drive pulley target axial thrust if said drive pulley target axial thrust is greater than said drive pulley necessary axial thrust;setting said drive pulley necessary axial thrust as the drive pulley target axial thrust if said drive pulley target axial thrust is less than said drive pulley necessary axial thrust, and, using said drive pulley necessary axial thrust, resetting the axial thrust deemed necessary at said driven pulley in order to change the transmission ratio to said target transmission ratio with said target rate of change of transmission ratio as the driven pulley target axial thrust; andperforming transmission ratio control using the newly set drive pulley and driven pulley target axial thrusts.