Patent ID: 6123644
Filing Date: 2000-09-26
Classification: F16H,Y10T

Abstract:
A method for controlling automatic downshifting in a vehicular automated mechanical transmission system (10) for a vehicle comprising a fuel-controlled engine (12), a multiple-speed mechanical transmission (14), and a controller (28) for receiving input signals (30) including one or more of signals indicative of direction of last shift, engine speed (ES), engaged gear ratio (GR) and vehicle speed (OS), and to process said input signals in accordance with logic rules to issue command output signals (32) to transmission system actuators including a transmission actuator (52) effective to shift said transmission, said control effective to command downshifts if, at current throttle position, the signal indicative of engine speed is less than a downshift reference value (ES.sub.DOWNSHIFT) for said current throttle position, said control setting a first default value (62) for said reference value and effective after an upshift to cause said reference value to be less than said default value by at least an anti-hunt offset value (72) until engine speed equals a reset reference value (ES=68), said method characterized by:(a) determining a value indicative of throttle position (THL);(b) determining a value indicative of vehicle acceleration (d/dt(OS)); and(c) if (i) throttle position is greater than a throttle reference value (THL>REF.sub.THL), and (ii) the vehicle is accelerating at less than a predetermined rate (d/dt(OS)<0), causing the absolute value of said anti-hunt offset value to decrease.