Main clutch reengagement control for a double clutch downshift

A master clutch reengagement control system for a vehicular automated mechanical transmission system (1 0) of the type comprising a multiple-speed change-gear mechanical transmission (12) drivingly connected to a fuel-controlled engine (14) by a friction master clutch (16), a throttle controller (30) operable by a vehicle operator to select fueling of the engine, a controller (44) for receiving input signals including an input signal (THL) indicative of setting of the throttle controller and an input signal (BRK) indicative of operation of a vehicle brake system (43), and for processing same in accordance with predetermined logic rules to issue command output signals to system operators including a transmission operator (48) for shifting the transmission, and a clutch operator (36) for engaging and disengaging said master clutch, said automated transmission system performing downshifts into a target gear ratio (GR.sub.T) in a sequence including reengaging the master clutch after engagement of the transmission in the downshift target gear ratio, said control system comprising:

• means for determining if the vehicle brake system is being operated (BRK=1 or BRK=0);
• means for determining a nominal clutch reengagement rate (CLU.sub.-- RATE) on the basis of input signals received by the controller;
• means for comparing throttle setting to a braking throttle reference value (REF.sub.1);
• and
• means effective, if the brake system is being operated (BRK=1) and if throttle setting is less than said braking throttle reference value, for commanding reengaging of said master clutch after engagement of the transmission in the downshift target gear ratio in a sequence comprising movement of said clutch at a faster rate than said nominal rate of incipient engagement to a point thereof and then further engagement at a braking reengagement rate (X * CLU.sub.-- RATE) slower than said nominal reengagement rate.

A control method for a vehicular automated mechanical transmission system (10) comprising a multiple-speed change-gear mechanical transmission (12) drivingly connected to a fuel-controlled engine (14) by a friction master clutch (16), a throttle controller (30) operable by a vehicle operator to select fueling of the engine, a controller (44) for receiving input signals including an input signal (THL) indicative of setting of the throttle controller and for processing same in accordance with predetermined logic rules to issue command output signals to system operators including a transmission operator (48) for shifting the transmission and a clutch operator (36) for engaging and disengaging said master clutch, said system performing downshifts into a downshift target gear ratio (GR.sub.T) in a sequence including reengaging the master clutch after engagement of the transmission in the downshift target gear ratio, said method comprising:

• determining a nominal clutch reengagement rate (CLU.sub.-- RATE) on the basis of input signals received by the controller;
• comparing throttle setting to a coasting throttle reference value (REF.sub.2);
• and
• if throttle setting is less than said coasting throttle reference value, commanding reengaging of said master clutch after engagement of the transmission in the downshift target gear ratio in a sequence comprising movement of said clutch at a rate faster than said nominal rate to a point of incipient engagement thereof and then further engagement at a coasting reengagement rate (Y * CLU.sub.-- RATE) slower than said nominal reengagement rate.

A control method for a vehicular automated mechanical transmission system (10) comprising a multiple-speed change-gear mechanical transmission (12) drivingly connected to a fuel-controlled engine (14) by a friction master clutch (16), a throttle controller (30) operable by a vehicle operator to select fueling of the engine, a controller (44) for receiving input signals including an input signal (THL) indicative of setting of the throttle controller and an input signal (BRK) indicative of operation of a vehicle brake system (43), and for processing same in accordance with predetermined logic rules to issue command output signals to system operators including a transmission operator (48) for shifting the transmission, and a clutch operator (36) for engaging and disengaging said master clutch, said system performing downshifts into a target gear ratio (GR.sub.T) in a sequence including reengaging the master clutch after engagement of the transmission in the downshift target gear ratio, said method comprising:

• determining if the vehicle brake system is being operated (BRK=1 or BRK=0);
• determining a nominal clutch reengagement rate (CLU.sub.-- RATE) on the basis of input signals received by the controller;
• comparing throttle setting to a braking throttle reference value (REF.sub.1);
• and
• if the brake system is being operated (BRK=1) and if throttle setting is less than said braking throttle reference value, commanding reengaging of said master clutch after engagement of the transmission in the downshift target gear ratio in a sequence comprising rapid movement of said clutch at a faster rate than said nominal rate to a point incipient engagement thereof and then further engagement at a braking reengagement rate (X * CLU.sub.-- RATE) slower than said nominal reengagement rate.