Patent ID: 6871131

Claim:
A method of changing gear in an automated transmission system of a motor vehicle including: a multi-ratio gearbox having at least two shafts including an input shaft and an output shaft; a take-up clutch located between the input shaft and an output shaft of an engine by which torque may be transmitted between the engine and the input shaft; a number of pairs of intermeshing gears, one gear of each pair being mounted in fixed rotational relationship with one of said shafts and the other gear of each pair being rotatably mounted with respect to another shaft; the rotatably mounted gears of each pair of gears having means for selectively rotatably securing the gears to said other shaft; a power shifting clutch being adapted to rotatably secure the rotatably mounted gear of a first pair of gears to said other shaft; and means for sensing the speed of the input shaft and the speed of the output shaft of the gearbox; in which when the vehicle is in motion, the take-up clutch will be engaged to transmit torque from the engine to the input shaft of the gearbox and the rotatably mounted gear of one pair of gears is rotatably secured to said other shaft to engage said pair of gears and transmit torque from the input shaft to the output shaft; said method comprising: a) engaging the power shifting clutch so that the torque transmitted through the currently engaged gear is gradually diverted through the power shifting clutch and said first pair of gears associated therewith; b) when the torque transmitted by the power shifting clutch is equal to the engine torque, within prescribed limits, the currently engaged gear is disengaged; c) following disengagement of the currently engaged gear, the power shifting clutch and/or the engine are controlled to increase the torque difference between the torque transmitted by the power shifting clutch and the torque produced by the engine, to a first predetermined value, so as to bring the synchronisation speed Δω towards zero, where: synchronisation speed Δω=ω mot −iω lsk where; ω mot =the input shaft speed; ω lsk =the output shaft speed; and i=the gear ratio of a target gear; d) after a first predetermined time period the power shifting clutch and/or engine being controlled to reduce the difference between the torque transmitted by the power shifting clutch and the torque produced by the engine so that the synchronisation speed and acceleration of the input shaft level off towards zero; and e) engaging the relatively rotatable gear of the target gear with said other shaft, when the synchronisation speed is at zero, within prescribed limits.