A method for operating a vehicle drive train (1) includes, during a downshift, disengaging at least one shift element (A through F) from a power flow of the transmission (5), guiding a power transmission capacity of a torque converter lockup clutch (4) to a level at which the torque converter lockup clutch (4) is in a non-slip operating condition during a positive engine override when a rotational speed of a prime mover (2) is guided towards a synchronous speed of a demanded desired ratio, and guiding the power transmission capacity of the torque converter lockup clutch (4)—no later than a point in time of the downshift at which the rotational speed of the prime mover (2) is equal to the synchronous speed of the desired ratio—to a level at which the torque converter lockup clutch (4) is transferred into a continuous slip operation due to torque.

A control apparatus for a vehicle provided with (i) a power source, (ii) drive wheels and (iii) a fluid transmission device disposed between the power source and the drive wheels and including a lockup clutch to which a fluid pressure is supplied. A feedback control is executed for correcting a command value of the fluid pressure by a correction amount such that an actual value of a slip amount of the lockup clutch becomes substantially equal to the target value of the slip amount in a slip control. When the actual value has been converged into a given range with respect to the target value, the correction amount is obtained, and the command value for a next execution of the slip control is corrected by learning with use of the obtained correction amount. The given range is set depending on the target value of the slip amount.

A continuously variable transmission (2) has a torque convertor (3) having a lock-up clutch (30) and a continuously variable transmission mechanism (5). A control unit (10) has a shift control unit (10C) configured to be able to perform a pseudo stepwise up-shift control that varies a transmission ratio of the continuously variable transmission mechanism (5) stepwise, a lock-up control unit (10A) configured to control an engagement state of the lock-up clutch (30), and a torque control command unit (10D) configured to perform a torque-down control of a driving source (1). When the engagement control of the lock-up clutch (30) and the pseudo stepwise up-shift control are performed at the same time, the torque control command unit (10D) configured to perform the torque-down control with a greater torque reduction amount.

A calibration method for a slip control arrangement of a driveline including a continuously variable transmission is described herein. The driveline includes a clutch that is so controlled as to slip when a torque higher than the usable torque attempts to pass through. Accordingly, the clutch prevents the prime mover from stalling. A calibration method to link a valve command value and a torque allowed to pass through the clutch includes preventing the vehicle from moving and increasing the pressure applied in the clutch while noting the torque % value developed by the prime mover.

A control device for a lock-up clutch includes a control unit, an abnormality determination unit, a release control unit and a prohibition unit. The control unit is configured to control an engagement state of a lock-up clutch, and to perform a slip lock-up control by performing a feedback control of an engagement hydraulic pressure to be a first slip amount during coasting. The abnormality determination unit is configured to determine an abnormality when a state continues with a slip amount being equal to or greater than a second slip amount. The release control unit is configured to release the lock-up clutch when the abnormality is determined. The prohibition unit is configured to allow the control unit to raise the engagement hydraulic pressure by a prescribed pressure, and to prohibit determination by the abnormality determination unit, when the transmission ratio is downshifted during coasting while the slip lock-up control is performed.

A work vehicle includes an engine, a drive wheel, a power transmission mechanism configured to transmit a driving power of the engine to the drive wheel, and a control unit configured to control the power transmission mechanism. The power transmission mechanism has a torque converter including a first clutch, and a second clutch coupled to the torque converter. The control unit controls an oil pressure supplied to the first clutch to a predetermined oil pressure when the second clutch is partially engaged.

A vehicle control method is provided for controlling a vehicle in which a clutch provided on a power transmission path between an engine and a drive wheel is disconnected when a shift range is a non-driving range and the clutch is connected when the shift range is a driving range. The vehicle control method controls the engine to a prescribed idling speed, controls engine torque to a negative torque by delaying an ignition timing of the engine; and causes the prescribed idling speed to drop within a prescribed amount of time needed for the clutch to switch from being disconnected to being connected when the shift range is switched from the non-driving range to the driving range.

Provided is a lockup control device and a lockup control method for a vehicle power transmission device provided with a fluid transmission device including a lockup clutch. The lockup clutch is controlled to perform slip-engagement such that a differential rotation between an input-side rotating member and an output-side rotating member of the fluid transmission device is a target differential rotation set in advance, and the target differential rotation is corrected based on transition of a heat accumulation amount applied to friction members of the lockup clutch.

A vehicle control device for a vehicle with a drive source and an automatic transmission including a friction engaging element for transmitting a driving force of the drive source to drive wheels by being engaged by a hydraulic pressure, wherein the vehicle control device is configured to perform an abnormality diagnosis of a solenoid valve for adjusting a hydraulic pressure to be supplied to the friction engaging element on the basis of a slip amount of the friction engaging element, and prohibit the abnormality diagnosis of the solenoid valve if a hydraulic pressure upstream of the solenoid valve is below a predetermined hydraulic pressure at which the friction engaging element is engaged, the hydraulic pressure upstream of the solenoid being a source hydraulic pressure to be adjusted by the solenoid valve.

A transmission system includes a fluid-coupling device, an electro-hydraulic control system, and a clutch. The fluid-coupling device includes an input coupled to an impeller, an output coupled to a turbine, and a stator disposed between the impeller and the turbine. The electro-hydraulic control system includes a flow valve disposed in fluid communication with the input and the output of the fluid-coupling device that is movable between at least a first position and a second position, at least one trim valve system fluidly coupled to the flow valve, and a solenoid disposed in fluid communication with the flow valve that is electrically controllable between an energized state and a de-energized state. The clutch is disposable in fluid communication with the flow valve and controllable between an applied position and an unapplied position.