Systems and methods for improving operation of a hybrid vehicle are presented. In one example, driveline operation may be adjusted in response to operating the hybrid vehicle in a four wheel drivel low gear range. The approaches may improve vehicle drivability and reduce driveline degradation.

A vehicle includes a powertrain and at least one controller programmed to, in response to a brake request and a shaft speed associated with a speed of the vehicle achieving a starting speed that is defined by a torque of the powertrain that changes with brake demand at a given shaft speed, reduce a regenerative torque limit that constrains regenerative braking torque over a blend-out duration based on the shaft speed.

In a vehicle equipped with a torque converter (4) having a lock-up clutch (3), learning control for obtaining a learning value (L_n) on the basis of meet-point information, with which the lock-up clutch (3) initiates torque transmission, is carried out. After acquiring the current learning detection value (M_n), a meet-point learning control unit (12c) calculates the current detection error (E_n) on the basis of the difference between the current learning detection value (M_n) and the previous learning value (L_(n1)) that is stored. When the current and previous detection errors (E_n) and (E_n1) have the same plus/minus sign, the current learning value correction amount is set to a larger value if the absolute value |(E_n1)| of the previous detection error (E_n1) is large than if the absolute value |(E_n1)| is small. The sum of the previous learning value (L_(n1)) and the current learning value correction amount is set as the present learning value (L_n).

In a vehicle on which a torque converter having a lock-up clutch is mounted between an engine and a transmission, a meet point learning controller is provided to perform learning control for obtaining a learning value based on information on a meet point at which the lock-up clutch starts torque transmission. The meet point learning controller estimates a LU transmission torque based on a difference between an engine torque signal value and a torque converter transmission torque when the lock-up clutch moves from a non-engaged state to an engaged state during traveling of the vehicle, and uses, as the meet point information, a meet point detection pressure at a time when the LU transmission torque estimated value is determined to have entered an upward trend.

In a vehicle equipped with a torque converter 4 having a lock-up clutch (3), learning control for obtaining a learning value (L_n) on the basis of meet-point information, with which the lock-up clutch (3) initiates torque transmission, is carried out. When the lock-up clutch (3) experiences a transition to an engaged state during travel, a meet-point learning control unit (12c) calculates an LU transmission torque estimate on the basis of the difference between the engine torque (engine torque signal value Te) and the torque converter transmission torque (.Math.Ne.sup.2). Excess clutch capacity is detected when the LU transmission torque estimate is greater than an excess capacity determination transmission torque threshold within a prescribed amount of time after an initial pressure (P_n) based on the learning value (L_n) is instructed. When excess clutch capacity is detected, a learning value correction that reduces the learning value (L_n) is carried out.

A vehicle includes a powertrain and a controller. The powertrain includes a transmission torque converter having a bypass clutch disposed between an electric machine and a drive wheel. The controller is programmed to adjust a closed-state torque capacity of the bypass clutch according and in proportion to the greater in absolute value of a negative impeller torque command to the torque converter and a negative regenerative braking torque request.

A transmission includes a housing, and a transmission input member. A torque converter includes a pump and a turbine. The turbine of the torque converter is connected to the transmission input member. A lock-up clutch selectively connects the pump and the turbine. A cover is connected to and rotatable with the pump. The cover at least partially defines an interior of the torque converter. A torque converter input member passes through the cover. A one way clutch interconnects the torque converter input member and the cover. An engine brake friction clutch is disposed within the interior of the torque converter. The engine brake friction clutch selectively interconnects the torque converter input member and the cover in torque communication to transfer a braking torque therebetween.

A method and an apparatus for controlling a hybrid electric vehicle including a dual clutch transmission are provided. The method for controlling a hybrid electric vehicle including a dual clutch transmission may include: determining whether an engine start condition is satisfied in a state in which an engine is stopped; determining whether a kick-down shift condition is satisfied when the engine start condition is satisfied; connecting a speed gear corresponding to a target gear stage to an output shaft corresponding to the target gear stage when the kick-down shift condition is satisfied; determining whether a lock-up condition of an engine clutch is satisfied when the engine start condition is satisfied; locking up the engine clutch when the lock-up condition of the engine clutch is satisfied; and locking up a shift clutch corresponding to the target gear stage when the engine clutch is locked up.

A vehicle includes a powertrain and at least one controller programmed to, in response to a brake request and a shaft speed associated with a speed of the vehicle achieving a starting speed that is defined by a torque of the powertrain that changes with brake demand at a given shaft speed, reduce a regenerative torque limit that constrains regenerative braking torque over a blend-out duration based on the shaft speed.

A vehicle includes an electric machine, battery, torque converter bypass clutch, drive wheel, and controller. The electric machine is configured to recharge the battery via regenerative braking. The torque converter bypass clutch is disposed between the electric machine and the drive wheel. The controller is programmed to, in response to a negative drive wheel torque command during a regenerative braking event, adjust a closed-state torque capacity of the torque converter bypass clutch based on the torque command.