Actuation system for transmission synchronizer providing regulated engagement pressure

In a transmission for a vehicle, comprising a rotary power input member, a rotary power output member, and a synchronizer for selectively torque-transmittingly connecting said power input member to said power output member, said synchronizer comprising a first rotary member rotatably around an axis and constantly torque-transmittingly connected with said power input member, a second rotary member rotatably around said axis and constantly torque-transmittingly connected with said power output member, a synchronizer sleeve rotatable around said axis and constantly torque-transmittingly connected with one of said first and second rotary members, said synchronizer sleeve being axially movable relative to said one rotary member so far as torque-transmittingly to mesh with the other of said first and second rotary members, and a synchronizer ring rotatable around said axis and torque-transmittingly connected with said one rotary member when said synchronizer sleeve is axially moved toward said other of said first and second rotary members, said synchronizer ring being frictionally engagable with said other rotary member so as to make rotations of said first and second rotary members approach to one another toward synchronization therebetween when frictionally pressed against said other rotary member, an actuation system, comprising:

• (a) an actuator which selectively drives said synchronizer sleeve and synchronizer ring together toward and away from said other rotary member so as, when said synchronizer sleeve and synchronizer ring are driven toward said other rotary member, first to engage said synchronizer ring frictionally with said other rotary member and then to engage said synchronizer sleeve as torque-transmittingly meshed with said other rotary member;
• and
• (b) a control system which controls operation of said actuator so as, when said synchronizer sleeve and synchronizer ring are driven toward said other rotary member, to vary the force of frictionally pressing said synchronizer ring against said other rotary member in relation to the difference of rotational speed between said first and second rotary members so that said force of frictional pressing is substantially lower when said difference of rotational speed substantially exists than a final value after said difference of rotational speed has substantially disappeared, wherein said force of frictional pressing is aburptly and substantially increased up to said final value at the time when said difference of rotational speed is reduced substantially to zero.