Torque-control system for automatic speed changer shiftable under load

Claim 1

In a transmission system shiftable under load provided with a gear-shifting stage comprising a friction coupling with relatively rotatable input and output members that are progressively interengageable by hydraulic fluid from a source provided with flow-regulating means, the combination therewith of: sensing means operatively coupled with said members for generating a measuring signal proportional to the relative rotary speed thereof calculated as an absolute difference of respective speeds of said members; computer means connected to said sensing means for emitting a precalculated reference signal proportional to a predetermined optimum angular acceleration assigned to said relative rotary speed; differentiation means connected to said sensing means for generating a monitoring signal proportional to a gradient of said relative rotary speed calculated as a differential quotient thereof with respect to time; comparison means with input connections to said computer means and to said differentiation means for emitting an error signal generally proportional to any deviation of said monitoring signal from said reference signal during progressive interengagement of said members; and electronic control means connected between said comparison means and said flow-regulating means for modifying a pressure of said hydraulic fluid in response to said error signal to reduce said deviation, said computer means being programmed to subdivide a range of relative rotary speeds between an initial maximum and zero into a plurality of subranges in which said angular acceleration varies substantially linearly at different rates, with a smooth transition of said relative rotary speed from one subrange to the next and a single change of sign of the time differential of said angular acceleration between the next-to-last subrange and the last subrange at the zero end of said range.