Patent ID: 6250172
Filing Date: 2001-06-26
Classification: F16H,Y10S,Y10T

Abstract:
A gear change (1) for a commercial vehicle of the type comprising:an input shaft (2);an output shaft (40):a compound transmission (34,35,38) interposed between said input shaft (2) and said output shaft (40) and comprising at least one main group (35) defining a plurality of main transmission ratios and an auxiliary group (34,38) with two auxiliary transmission ratios defining respective pluralities of gear ratios of said gear change apparatus in combination with the main transmission ratios, said auxiliary group (34,38) comprising a coupling member (13,44) which can move between a first coupling position, in which a first auxiliary transmission ratio is activated, and a second coupling position, in which a second auxiliary transmission ratio is activated;an actuator (37, 45) for controlling said movable coupling member (13,44), anda control unit (47) adapted to generate control signals for said actuator (37,45) in response to a plurality of input signals (s.sub.w, s.sub.s, s.sub.r) which are representative of operating parameters of said gear change apparatus and of the position of manual selector (56,57) associated with said gear change (1),characterized in that said actuator (37) is adapted to adopt three stable positions which correspond, respectively, to said first position, to said second position and to a third neutral position of said movable coupling member (13), which is intermediate with respect to said first and second positions, in which said input shaft (2) and said output shaft (40) are uncoupled from one another; said control unit (47) comprising means (52) for comparing the speed of rotation of said input shaft (2) following the engagement of a new gear ratio with a predetermined range ofpredetermined values, and means (54) for generating control signs (s.sub.c,) to arrange said actuator (37) in said third position in the event that said speed is outside said predetermined range of predetermined values.