An automatic transmission system includes a housing containing automatic transmission fluid (ATF), a plurality of clutches configured to be engaged to generate gear ratios corresponding to forward speeds of the automatic transmission, wherein one clutch of the plurality of clutches is a friction clutch movable between a disengaged state, an engaged state utilized to create one or more gear ratios of the automatic transmission, and a slippingly engaged state between the disengaged state and the engaged state where the friction clutch is not engaged to create a gear ratio of the automatic transmission, and a controller configured to selectively move the friction clutch to the slippingly engaged state when the friction clutch is not being utilized to generate the one or more gear ratios, such that the friction clutch generates heat from friction to thereby rapidly heat the ATF in the housing and improve operating efficiency of the transmission.

A method of determining automatic transmission lubrication fluid flow rates corresponding to a running vehicle without direct oil flow measurements is disclosed. A set of in-vehicle clutch torques for a chosen clutch pack during a gear shift event for a set of shift conditions is obtained. A series of bench tests at various clutch-pack clearances and oil-flow rates for the set of shift conditions are performed. The clearances and oil-flow rates are adjusted in response to the measured magnitudes exceeding thresholds. In-vehicle transmission lubrication oil-flow rates are estimated at the chosen clutch pack for the set of shift conditions when the bench-test and in-vehicle clutch torques are less than the thresholds. The steps are reproduced for other engine conditions and fluid temperatures corresponding to other transmission gear positions. A functional map of in-vehicle oil flow rates are produced, and the transmission is adjusted based on the map.

A transmission for an energy storage and recovery system comprises a variable slip transmission and a clutch arranged to transmit drive while slipping. The level of torque transmitted through the slipping clutch is dependent on the clutch force but is independent of the clutch slip speed. Preferably the clutch is provided by a plurality of clutches connected in parallel in a range extender. When drive is transferred between clutches in parallel, the clutch forces of both clutches are controlled to maintain the total torque transmitted by the clutches. This reduces torque fluctuations at the energy source/sink during clutch transfer. Where there are two slipping clutches in series, one clutch is controlled to provide the required torque and the other clutch is controlled in response to a clutch slip speed. This helps to control the speed of rotation of the mass between the clutches.

A transmission for an energy storage and recovery system comprises a variable slip transmission and a clutch arranged to transmit drive while slipping. The level of torque transmitted through the slipping clutch is dependent on the clutch force but is independent of the clutch slip speed. Preferably the clutch is provided by a plurality of clutches connected in parallel in a range extender. When drive is transferred between clutches in parallel, the clutch forces of both clutches are controlled to maintain the total torque transmitted by the clutches. This reduces torque fluctuations at the energy source/sink during clutch transfer. Where there are two slipping clutches in series, one clutch is controlled to provide the required torque and the other clutch is controlled in response to a clutch slip speed. This helps to control the speed of rotation of the mass between the clutches.

A transmission for an energy storage and recovery system is disclosed. A variable slip transmission and a clutch arranged to transmit drive while slipping. The level of torque transmitted through the slipping clutch is dependent on the clutch force but is independent of the clutch slip speed. Preferably the clutch is provided by a plurality of clutches connected in parallel in a range extender. When drive is transferred between clutches in parallel, the clutch forces of both clutches are controlled to maintain the total torque transmitted by the clutches. This reduces torque fluctuations at the energy source/sink during clutch transfer. Where there are two slipping clutches in series, one clutch is controlled to provide the required torque and the other clutch is controlled in response to a clutch slip speed. This helps to control the speed of rotation of the mass between the clutches.

A vehicle includes a transmission and a controller. The transmission has clutches and multiple speed ratios that are established during gear upshifts upon torque being transferred from off-going to oncoming clutches. The controller is programmed to, in response to a difference between actual and target times of a desired flare at a transmission input exceeding a threshold during an upshift, adjust the torque of the off-going clutch during a torque transfer phase of a subsequent upshift based on the difference.

An automatic transmission system includes a housing containing automatic transmission fluid (ATF), a plurality of clutches configured to be engaged to generate gear ratios corresponding to forward speeds of the automatic transmission, wherein one clutch of the plurality of clutches is a friction clutch movable between a disengaged state, an engaged state utilized to create one or more gear ratios of the automatic transmission, and a slippingly engaged state between the disengaged state and the engaged state where the friction clutch is not engaged to create a gear ratio of the automatic transmission, and a controller configured to selectively move the friction clutch to the slippingly engaged state when the friction clutch is not being utilized to generate the one or more gear ratios, such that the friction clutch generates heat from friction to thereby rapidly heat the ATF in the housing and improve operating efficiency of the transmission.

A vehicle includes a transmission and a controller. The transmission has clutches and multiple speed ratios that are established during gear upshifts upon torque being transferred from off-going to oncoming clutches. The controller is programmed to, in response to a difference between actual and target times of a desired flare at a transmission input exceeding a threshold during an upshift, adjust the torque of the off-going clutch during a torque transfer phase of a subsequent upshift based on the difference.

A method of determining automatic transmission lubrication fluid flow rates corresponding to a running vehicle without direct oil flow measurements is disclosed. A set of in-vehicle clutch torques for a chosen clutch pack during a gear shift event for a set of shift conditions is obtained. A series of bench tests at various clutch-pack clearances and oil-flow rates for the set of shift conditions are performed. The clearances and oil-flow rates are adjusted in response to the measured magnitudes exceeding thresholds. In-vehicle transmission lubrication oil-flow rates are estimated at the chosen clutch pack for the set of shift conditions when the bench-test and in-vehicle clutch torques are less than the thresholds. The steps are reproduced for other engine conditions and fluid temperatures corresponding to other transmission gear positions. A functional map of in-vehicle oil flow rates are produced, and the transmission is adjusted based on the map.

A transmission for an energy storage and recovery system is disclosed. A variable slip transmission and a clutch arranged to transmit drive while slipping. The level of torque transmitted through the slipping clutch is dependent on the clutch force but is independent of the clutch slip speed. Preferably the clutch is provided by a plurality of clutches connected in parallel in a range extender. When drive is transferred between clutches in parallel, the clutch forces of both clutches are controlled to maintain the total torque transmitted by the clutches. This reduces torque fluctuations at the energy source/sink during clutch transfer. Where there are two slipping clutches in series, one clutch is controlled to provide the required torque and the other clutch is controlled in response to a clutch slip speed. This helps to control the speed of rotation of the mass between the clutches.