Servo operation apparatus for a transmission

A servo operation apparatus for a transmission comprising:

• an input shaft to which the shift-change operation force is mechanically transmitted from a shift lever;
• a servo unit for boosting said shift-change operation force by feeding a working fluid from a working fluid feed source to a servo chamber of the synchronizing side and to a servo chamber of the drag side divided by a piston inscribing a cylinder in the apparatus body;
• an output shaft to which said piston is secured as a unitary structure and which is disposed to move relative to said input shaft and transmits the shift-change operation force boosted by said servo unit to a transmission;
• a valve device which switchingly feeds the working fluid to the servo chamber of the synchronizing side from the start of the shift to the completion of the synchronization and to the servo chamber of the drag side from the completion of the synchronization to the completion of the shift depending upon the relative positions of said input shaft and said output shaft;
• and
• a first working fluid feed control means which feeds the working fluid in such a manner that the pressure of the working fluid in the servo chamber of the drag side is raised with a steep gradient in the former half until a predetermined initially raised pressure value is reached and, thereafter, is raised in the latter half with a gradient less steep than that of said former half.