Patent ID: 6910989

Claim:
A method for increasing brake efficiency of a vehicle with a hydrodynamic retarder, in which a rotational speed of a motor is increased by command for downshifting in such a manner that due to an increased rotational speed of the motor, a quantity of available circulating cooling fluid is increase to facilitate necessary retarder braking, the method comprising the steps of: ( 20 A) determining a necessity ( 16 N) of a downshift command ( 16 ) from at least one of an actual braking efficiency ( 22 ) of the retarder ( 16 ), a driving condition ( 24 ), and a potential for cower ( 26 ) of a vehicle cooling system ( 28 ); ( 20 B) determining an actual braking efficiency ( 22 ) from at least one of an actual braking moment ( 32 ), a braking power ( 34 ), a retarder inlet pressure ( 36 ), a retarder outlet pressure ( 38 ) and a regulating flow ( 40 ); ( 20 C) determining an actual driving condition ( 24 ) from at least one of an actual transmission output shaft rotational speed ( 42 ), a rotational wheel speed ( 44 ) of a wheel ( 46 ), a motor rotational speed ( 48 ) of motor ( 14 ), a clutch rotational speed ( 50 ) of a clutch ( 52 ), a vehicle speed ( 54 ) of the vehicle ( 10 ) and also from at least one of a change in rotational speed ( 56 ), a change in the vehicle speed ( 58 ), a topography ( 60 ), and a weight ( 62 ) of the vehicle ( 10 ) with respect to the topography ( 60 ); ( 20 D) determining the potential for power ( 26 ) of the vehicle cooling system ( 28 ) by at least one of a temperature ( 64 ) of the cooling system ( 28 ), a change of temperature ( 66 ) of the cooling system ( 28 ), a function of time ( 66 ), the rotational speed ( 48 ) of the motor ( 14 ), a pressure ( 70 ) of the cooling circulation system ( 28 ), a shift position ( 72 ), a clutch state ( 74 ) and a rotational speed ( 76 ) of a water pump ( 78 ); and, ( 20 E) when the necessity of a downshift command ( 16 N) is determined, issuing the downshift command ( 16 ); and ( 20 F) in response to the issued command ( 16 ) for downshifting, increasing a rotational speed ( 48 ) of the motor ( 14 ) in such a manner that a quantity ( 80 ) of available circulating cooling fluid ( 18 ) is increase to facilitate necessary retarder ( 12 ) braking.