Abstract: A vehicle includes an engine and driven wheels each having an associated friction brake. A brake pedal is operable to engage the friction brakes. The vehicle includes a transmission having an input shaft driveably connected to the engine, an output element driveably connected to the driven wheels, and a gear mechanism adapted to establish at least one torque flow path between the input shaft and the output element. The transmission further includes a shift element that interrupts the torque flow path when disengaged. A gear selector is disposed in the passenger cabin and includes at least one forward-drive position, a reverse position, and a neutral position. At least one vehicle controller is configured to, in response to the gear selector being in the forward-drive position, a speed of the vehicle being zero, the vehicle being within a first predefined distance of a stoplight, and the brake pedal being depressed, disengage the shift element to put the transmission in neutral idle.

Abstract: A transmission controller implements a neutral idle feature to reduce fuel consumption. A brake controller implements a Hill Start Assist feature to prevent roll-back when a vehicle is launching on an uphill grade. The transmission controller and the brake controller communicate to implement these features in a synergistic manner. Within certain road grade ranges, the transmission requests Hill Start Assist before activating neutral idle and does not activate neutral idle until it receives confirmation that Hill Start Assist is active. The transmission controller provides a powertrain torque estimate to the brake controller which the brake controller uses to determine when to release the brakes during an assisted start.

Abstract: A vehicle includes an engine and driven wheels each having an associated friction brake. A brake pedal is operable to engage the friction brakes. The vehicle includes a transmission having an input shaft driveably connected to the engine, an output element driveably connected to the driven wheels, and a gear mechanism adapted to establish at least one torque flow path between the input shaft and the output element. The transmission further includes a shift element that interrupts the torque flow path when disengaged. A gear selector is disposed in the passenger cabin and includes at least one forward-drive position, a reverse position, and a neutral position. At least one vehicle controller is configured to, in response to the gear selector being in the forward-drive position, a speed of the vehicle being zero, the vehicle being within a first predefined distance of a stoplight, and the brake pedal being depressed, disengage the shift element to put the transmission in neutral idle.

Abstract: Systems and methods for reducing perception of transitions from shifting a transmission from neutral to drive are described. In one example, the transmission is shifted from neutral to drive in response to brake pedal motion before the brake pedal is fully released so that timing of pressurizing clutches and engaging a forward gear is advanced to occur while the brake pedal is still applied.

Abstract: A method of controlling a Continuously Variable Transmission (CVT) simulates a step-ratio transmission upshift. To simulate a step-ratio torque phase, the input torque is gradually reduced before beginning to change the variator ratio. Then, as the variator ratio is changed, the input torque is gradually increased to compensate for the decreasing torque ratio, simulating the relatively constant output torque of an inertia phase of a step-ratio upshift.

Abstract: A controller and a control strategy for a hybrid electric vehicle having a traction motor between an engine and an automatic transmission include maintaining a bypass clutch of a torque converter in an engaged position and applying a motor torque from a traction motor to the torque converter such that slip of the torque converter does not otherwise reach zero while the bypass clutch is maintained in the engaged position.

Abstract: A method of controlling a Continuously Variable Transmission (CVT) simulates a step-ratio transmission upshift. To simulate a step-ratio torque phase, the input torque is gradually reduced before beginning to change the variator ratio. Then, as the variator ratio is changed, the input torque is gradually increased to compensate for the decreasing torque ratio, simulating the relatively constant output torque of an inertia phase of a step-ratio upshift.

Abstract: A vehicle is provided with a powertrain including a battery-powered electric motor, an internal combustion engine, a transmission, and a powertrain controller. The controller is programmed to permit an upshift of a transmission gear ratio while a powertrain torque demand is less than a forecasted available powertrain torque sustainable over a predetermined upcoming duration of time. The controller is also programmed to inhibit an upshift while the torque demand exceeds the forecasted available powertrain torque to reduce successive gear shifts. The controller may be further programmed to, in response to battery a state of charge being less than a threshold, reduce the forecasted available powertrain torque by an amount sufficient to provide a recharge to a battery. The controller may be further still programmed to reduce the forecasted available powertrain torque by an amount sufficient to restart the engine while the powertrain is operating in an engine-off traction mode.

Abstract: A vehicle includes a transmission and a controller. The controller is configured to receive a torque request, calculate a Specific Fuel Consumption (SFC) for satisfying the torque request in an initial gear and in an alternate gear, and command the transmission to shift from the initial gear into the alternate gear in response to the calculated SFC for satisfying the torque request in the alternate gear being less than the calculated SFC for satisfying the torque request in the initial gear.

Abstract: A vehicle includes an engine with an associated engine-speed sensor, and wheels each having a respective wheel-speed sensor. The vehicle also includes a continuously variable transmission (CVT) coupled to the engine and configured to operate at variable input-to-output ratios. At least one controller is programmed to reduce the operating ratio of the CVT in response to the engine-speed sensor indicating the engine is operating at idle speed and the wheel-speed sensor indicating the velocity is approximately zero. This provides less noise, vibration and harshness in the vehicle due to the reduced ratio that is possible during conditions in which a vehicle launch in that reduced ratio may not be acceptable.

Abstract: A hybrid vehicle powertrain is configured to provide a regenerative-braking torque limit on a transmission during a regenerative-braking downshift. The regenerative-braking downshift event has sequential boost, start, torque, inertia, and end phases. The transmission may be operated in absence of a regenerative-braking torque limit during the boost and start phases to recapture more energy. The transmission may be operated with a regenerative-braking torque limit during the torque and inertia phases to protect for an input shaft speed dip that may occur without the limit. The limit may be removed once the regenerative-braking downshift event is completed.

Abstract: A method for controlling regenerative braking in a hybrid electric powertrain includes using an e-pump to supply fluid to a transmission provided an indication that a torque converter clutch disengagement will occur under current powertrain operating conditions is present, and discontinuing use of the e-pump and using a mechanical pump to supply fluid to the transmission provided the indication that a torque converter clutch disengagement will occur under current powertrain operating conditions is absent.

Abstract: A vehicle includes a transmission and a controller. The controller is configured to receive a torque request, calculate an SFC for satisfying the torque request in an initial gear and in an alternate gear, and command the transmission to shift from the initial gear into the alternate gear in response to the calculated SFC for satisfying the torque request in the alternate gear being less than the calculated SFC for satisfying the torque request in the initial gear.

Abstract: A vehicle includes a powertrain having an electric machine, and friction brakes configured to resist rotation of a vehicle wheel. The further includes at least one controller programmed to (i) issue a command for the electric machine to apply a regenerative torque to decelerate the vehicle in response to driver braking demand, and (ii) cause both a decay in the regenerative torque and a countervailing increase in the resistance of the friction brakes when vehicle speed is reduced to less than a first threshold such that braking demand is substantially satisfied by only the friction brakes when the vehicle speed is less than a second threshold.

Abstract: A vehicle includes a powertrain having an electric machine configured to selectively apply regenerative torque to cause deceleration in response to braking demand; the powertrain further including a torque converter configured to decouple the electric machine from wheels of the vehicle. The vehicle is also provided with a controller programmed to, during a regenerative braking event, receive a signal defining a regenerative torque limit, and in response to a fault condition associated with the regenerative torque limit, generate a replacement regenerative torque limit based upon a torque converter open speed to decrease roughness during transitions into and out of regenerative braking.

Abstract: A control system including a method and apparatus for operating a hybrid vehicle. A disconnect clutch selectively separates an electric machine from a combustion engine. If a wide open throttle or high torque command is requested and the combustion engine is shut down, a 12 volt starter may be used to start the combustion engine while disconnected from the electric machine and all of the electric machine torque available may be used for traction.

Abstract: Impeller speed, which is difficult to measure when a torque converter includes an impeller clutch, is estimated based on a known relationship among impeller speed, turbine speed, and turbine torque. Turbine torque may be directly measured by a turbine torque sensor or estimated based on other measurements such as output shaft torque or vehicle acceleration. The relationship is stored in a controller in terms of the coefficients of a second order polynomial relating turbine torque to impeller speed and turbine speed. A slip speed is calculated based on a measured input shaft speed and the estimated impeller speed. Closed loop control is used to adjust the impeller clutch torque capacity to maintain a target slip.

Abstract: A control system including a method and apparatus for operating a hybrid vehicle. A disconnect clutch selectively separates an electric machine from a combustion engine. If a wide open throttle or high torque command is requested and the combustion engine is shut down, a 12 volt starter may be used to start the combustion engine while disconnected from the electric machine and all of the electric machine torque available may be used for traction.

Abstract: Regenerative torque is limited for a hybrid electric powertrain of a vehicle. A transmission controller determined torque limit is validated by a vehicle controller. The vehicle controller validates the torque limit using, individually or in combination, an actual status of a torque converter clutch, a detected status of the torque converter clutch, or a speed of the vehicle.

Abstract: One exemplary aspect of this disclosure relates to a method including the step of controlling a level of regenerative torque to at least partially meet a braking request. The level of regenerative torque is gradually introduced at a controlled rate.