Method of braking in hybrid vehicle
AssigneeFord Global Technologies, LLC
InventorsBernard D. Nefcy, Francis Thomas Connolly, Daniel Scott Colvin
Life of this patent
Estimating the term…
Abstract
A method of operating a hybrid electric vehicle coordinates operation of an internal combustion engine, a motor, and friction brakes to mitigate a driveline lash crossing without delaying generation of negative torque. In response to a request to transition from positive torque to negative torque, the engine and motor are controlled to rapidly reduce powertrain torque to a small positive value, slowly reduce powertrain torque through the driveline lash zone, and then rapidly reduce powertrain torque to the target. To avoid delay, the friction brakes are applied in a coordinated manner to supply the negative torque during the transition.
Claims13
A hybrid electric vehicle comprising:
- a driveline configured to deliver a powertrain torque to vehicle wheels;
- friction brakes configured to deliver a braking torque to the vehicle wheels;
- an internal combustion engine configured to deliver positive torque to the driveline;
- an electric motor configured to alternately deliver positive and negative torque to the driveline;
- and
- a controller programmed to respond to a request to transition from positive wheel torque to negative wheel torque by
- commanding the engine and electric motor to reduce the powertrain torque from an initial positive value to a positive threshold value at a first rate of change,
- commanding the brakes to exert a brake torque while commanding the engine and electric motor to reduce the powertrain torque from the positive threshold value to a negative threshold value at a second rate of change having a magnitude less than a magnitude of the first rate of change to mitigate a lash crossing disturbance, and
- commanding the brakes to increase the brake torque to zero while commanding the electric motor to reduce the driveline torque from the negative threshold value to a target negative value at a third rate of change having a magnitude greater than the magnitude of the second rate of change.
A method of transitioning from positive wheel torque to negative wheel torque in a hybrid electric vehicle comprising:
- reducing a powertrain torque to a positive threshold value;
- exerting a brake torque while further reducing the powertrain torque through a zero level at a reduced rate of change of powertrain torque;
- and
- increasing the brake torque in conjunction with further reducing the powertrain torque to maintain a constant negative total wheel torque.
A method of operating a vehicle comprising:
- at regular intervals,
- commanding an engine and a motor to deliver a powertrain torque equal to a maximum of a Net Wheel Torque Demand (NWTD) and a Regenerative Torque Limit (RTL), and
- commanding friction brakes to deliver a braking torque equal to a minimum of zero and a difference between the NWTD and the RTL;
- and
- in response to NWTD changing from positive to negative,
- reducing the RTL from a positive threshold to a negative threshold at a first rate to mitigate a lash crossing disturbance.
Dependencies are inferred from the claim text.