Method for controlling a power assisted propulsion system in a motor vehicle

32) A method for controlling a power assisted propulsion system (4) in a motor vehicle (1) such that a transition from a higher gear to a lower gear is performed thus anticipating the effect of exhaust brake;

• the propulsion system (4) comprises an internal combustion engine (5) provided with a drive shaft (6) and a power assisted transmission comprising in turn:
• a power assisted mechanical gearbox (12) operated by a first servo control (16, 17) and provided with a primary shaft (13) connectable to the drive shaft (6) and a secondary shaft (14) connected to a transmission shaft (8) which transmits motion to the driving wheels (3);
• a power assisted clutch (15) operated by at least one second servo control (18) and interposed by the driving shaft (6) and the primary shaft (13) of the gearbox (12) to connect and disconnect the drive shaft (6) to the primary shaft (13) of the gearbox (12);
• a power assisted brake (23) operated by at least one third servo control (24);
• and
• an epicycloidal gear (19) having three rotating elements (20, 21, 22):
• a first rotating element (20) connected to the drive shaft (6), a second rotating element (21) connected to the secondary shaft (14) of the gearbox, and a third rotating element (22) connected to the brake (23);
• the control method comprises the steps of:
• opening the clutch (15) to separate the primary shaft (13) of the gearbox (12) of the drive shaft (6);
• disengaging the higher gear;
• engaging the lower gear;
• and
• closing the clutch (15) to connect the primary shaft (13) of the gearbox (12) to the drive shaft (6);
• the control method being characterized in that it comprises the further steps of:
• determining the order of a desired value of exhaust brake torque to be applied to the driving wheels (3) as a function of the lower gear to be engaged, the current motion of the motor vehicle (1), and/or the commands from the driver;
• actuating the brake (23) simultaneously to the opening of the clutch (15) to transmit through the epicycloidal gear (19) from the secondary shaft (14) of the gearbox (12) to the drive shaft (6) a torque substantially equal to the desired value of exhaust brake torque to be applied to the driving wheels (3);
• determining the value of angular speed (ω1) of the primary shaft (13) set by the lower gear and by the current motion of the motor vehicle (1);
• driving the internal combustion engine (5) such that, when the clutch (15) is closed, the drive shaft (6) has an angular speed (ωm) equal to the angular speed (ω1) of the primary shaft (13) set by the lower gear and by the current motion of the motor vehicle (1);
• and
• releasing the brake (23) simultaneously to the closing of the clutch (15) to interrupt the transfer of torque through the epicycloidal gear (19) from the secondary shaft (14) of the gearbox to the drive shaft (6).

33) A power assisted transmission (7) for a power assisted propulsion system (4) in a motor vehicle (1);

• the power assisted transmission (7) comprises:
• a power assisted mechanical gearbox (12) operated by at least one servo control (16, 17) and provided with a primary shaft (13) connectable to the drive shaft (6) and a secondary shaft (14) connected to a transmission shaft (8) which transmits motion to the driving wheels (3);
• a power assisted clutch (15) operated by at least one servo control (18) and interposed between the drive shaft (6) and the primary shaft (13) of the gearbox (12) to connect and disconnect the drive shaft (6) to the primary shaft (13) of the gearbox (12);
• a power assisted brake (23);
• and
• an epicycloidal gear (19) having three rotating elements (20, 21, 22):
• a first rotating element (20) connected to the drive shaft (6), a second rotating element (21) connected to the secondary shaft (14) of the gearbox, and a third rotating element (22) connected to the brake (23);
• the power assisted transmission (7) being characterized in that the gear ratios (7) of the epicycloidal gear (19) are dimensioned such that the third rotating element (22) of the epicycloidal gear (19) rotates 10 with an opposite direction with respect to the first rotating element (20) of the epicycloidal gear (19) when a lower gear than the intermediate gear is engaged in the gearbox and rotates with the same direction with respect to the first rotating element (20) of the epicycloidal gear (19) when a higher gear than the intermediate gear is engaged in the gearbox (12).

48) A power assisted transmission (7) for a power assisted propulsion system (4) in a motor vehicle (1);

• the power assisted transmission (7) comprises:
• a power assisted mechanical gearbox (12) operated by at least one servo control (16, 17) and provided with a primary shaft (13) connectable to the drive shaft (6) and a secondary shaft (14) connected to a transmission shaft (8) which transmits motion to the driving wheels (3);
• and
• a power assisted clutch (15) operated by at least one second servo control (18) and interposed between the drive shaft (6) and the primary shaft (13) of the gearbox (12) to connect and disconnect the drive shaft (6) to the primary shaft (13) of the gearbox (12);
• the power assisted transmission (7) being characterized in that it comprises:
• a pump (29) actuated by the drive shaft (6) or by the primary shaft (13) of the gearbox (12);
• a hydraulic accumulator (30) containing a fluid which is pressurized by the pump (29);
• and
• a hydraulic engine (31) actuated by the pressurized fluid and adapted to transmit torque to the secondary shaft (14) of the gearbox (12) or to the transmission shaft (8).

49) A power assisted transmission (7) for a power assisted propulsion system (4) in a motor vehicle (1);

• the power assisted transmission (7) comprises:
• a power assisted mechanical gearbox (12) operated by at least one servo control (16, 17) and provided with a primary shaft (13) connectable to the drive shaft (6) and a secondary shaft (14) connected to a transmission shaft (8) which transmits motion to the driving wheels (3);
• and
• a first power assisted clutch (15) operated by at least one servo control (18) and interposed between the drive shaft (6) and the primary shaft (13) of the gearbox (12) to connect and disconnect the drive shaft (6) to the primary shaft (13) of the gearbox (12);
• the power assisted transmission (7) being characterized in that it comprises:
• a chain (33) of gears, which transmits motion directly from the drive shaft (6) to the secondary shaft (14) of the gearbox (12);
• and
• a second power assisted clutch (34) driven by at least one servo control (35) and interposed along the chain (33) of gears to connect and disconnect the drive shaft (6) to the secondary shaft of the gearbox (12).