Patent ID: 6814689
Filing Date: 2004-11-09
Classification: F16H,Y10T

Abstract:
A hydraulic control apparatus of an automatic transmission provided with a plurality of friction engagement elements for gear change, which are engaged when a hydraulic pressure is delivered thereto and released when the hydraulic pressure is drained therefrom, said hydraulic control apparatus comprising:an operating condition detector detecting operating conditions of said automatic transmission; and a control unit receiving signals from said operating condition detector and controlling delivery and drain of the hydraulic pressure for each of said plurality of friction engagement elements for gear change, respectively; wherein said control unit:periodically delivers the hydraulic pressure to the friction engagement elements in released states out of said plurality of friction engagement elements for gear change, to discharge air mixed into a hydraulic circuit; switches a duty ratio in said periodic hydraulic pressure delivery to a plurality of different values according to said operating conditions; and computes an achievement ratio of air discharge per each of said plurality of duty ratios, and when a sum of said achievement ratios reaches a predetermined value or above, terminates the periodic delivery of hydraulic pressure for air discharge.