Patent ID: 7546196

Claim:
A line pressure control apparatus of a belt-drive continuously variable transmission employing a primary variable-width pulley of a driving pulley side, a secondary variable-width pulley of a driven pulley side, a drive belt running in the primary and secondary pulleys, and a shift actuator, and whose target transmission ratio is achieved by varying V-groove widths of the primary and secondary pulleys by way of a differential pressure between primary and secondary pulley pressures, both originating from line pressure, the differential pressure being created by bringing the shift actuator into a control position corresponding to the target transmission ratio, comprising: a vehicular information detector that detects engine-and-vehicle operating conditions; a hydraulic modulator that regulates the primary and secondary pulley pressures; a control unit being configured to be electrically connected to the vehicular information detector and the hydraulic modulator, for automatically controlling the hydraulic actuator depending on the operating conditions; the control unit comprising a processor programmed to perform the following, (a) determining a theoretical transmission ratio based on the operating conditions; (b) calculating the target transmission ratio based on the theoretical transmission ratio, taking account of at least a hardware response delay; (c) converting the target transmission ratio into a reference-model operative position of the shift actuator; (d) calculating an actual transmission ratio as a ratio of a rotational speed of the primary pulley to a rotational speed of the secondary pulley; (e) converting the actual transmission ratio into an actual-transmission-ratio related operative position of the shift actuator; (f) calculating a positional deviation between the reference-model operative position and the actual-transmission-ratio related operative position; and (g) correcting the line pressure in a manner so as to reduce the positional deviation.