Patent ID: 8894521
Filing Date: 2014-11-25
Classification: F16H

Abstract:
1. A power transmission device comprising: a belt-type continuously variable transmission that includes a first pulley that is connected to an input shaft, a second pulley that is connected to an output shaft, and a belt that is passed around both of the pulleys, the belt-type continuously variable transmission continuously varying, by varying a groove width of the first pulley and a groove width of the second pulley, power that is input to the input shaft and outputting the power to the output shaft; a first fluid pressure cylinder that is capable of varying the groove width of the first pulley using fluid pressure; a second fluid pressure cylinder that is capable of varying the groove width of the second pulley using fluid pressure and that does not have a cancel chamber; a pressure-adjustment and pressure-feed device that supplies a working fluid to a first fluid pressure cylinder side and a second fluid pressure cylinder side in conjunction with pressure adjustment; a fluid outflow/inflow device that allows and cuts off an inflow of the working fluid to the first fluid pressure cylinder from the pressure-adjustment and pressure-feed device and that allows and cuts off a discharge of the working fluid from the first fluid pressure cylinder; and a control unit that controls the pressure-adjustment and pressure-feed device based on a fluid pressure that is obtained from a thrust that is required for the second pulley in accordance with a driving state and that, by controlling the pressure-adjustment and pressure-feed device in this manner, controls the fluid outflow/inflow device such that a gear ratio is varied within a permitted gear ratio range in accordance with the fluid pressure that is pressure-fed from the pressure-adjustment and pressure-feed device in conjunction with the pressure adjustment, wherein