A device, system, and method for controlling transmission torque to provide hill ascent and/or descent assistance to a vehicle includes applying a clutch hold pressure to one or more clutches of a transmission to lock an output shaft of the transmission to resist roll-back of the vehicle. The clutch hold pressure is applied based on one or more of a transmission output speed signal, an engine throttle signal, and a vehicle brake signal.

An object of the present invention is to provide a vehicle parking lock system that realizes a parking lock with a positive user perception, and enables energy and cost reductions without complex control and with a simple configuration. The object is achieved by a selectable clutch configured to be switchable between four operating modes and provided to one of an input shaft, an output shaft, and an intermediate shaft of a transmission. The operating mode of the selectable clutch is controlled based on detection signals of a plurality of sensors to prevent an unintended movement of the vehicle when the vehicle is stationary.

A control device (12) for a stepped transmission mechanism is configured to perform an interlock by engaging a first clutch (32) and increasing hydraulic pressure of a second clutch (33) up to a first predetermined pressure (P1) such that an output shaft of the transmission mechanism is fixed, after an idle-stop condition including at least a requirement that a vehicle is stationary was satisfied and before a stop of an engine (1). The control device includes a gradient detecting section (12a, 47) that detects a gradient (R) of a road surface on which the vehicle is stationary; and a hydraulic control section (12c) that performs a slipping interlock by reducing the hydraulic pressure to a second predetermined pressure (P2), if the gradient R detected by the gradient detecting section is lower than or equal to a predetermined value (R.sub.TH) during the interlock and before the stop of the engine.

A control method for preventing backward slipping of a vehicle includes a range detection step in which a controller detects a range position of a shift lever, a gradient comparison step in which the controller compares a gradient of a road with a predetermined reference gradient when it is determined that the position of the shift lever is the D range, a stop state check step where the controller checks a brake and a driving state of the vehicle when it is determined at the gradient comparison step that the gradient of the road is equal to or greater than the reference gradient, and an inter-lock implementation step in which the controller engages multiple gears on an identical shaft when it is determined at the stop state check step that the brake is on and the vehicle has stopped.

A method of starting or holding a mobile vehicle and, in particular, a working machine. The method determines whether the vehicle is rolling backward on an inclined surface and, as a function of that knowledge, the rotational speed of the drive engine is increased, or a downshift by one gear is carried out in the transmission.

A required traction force determining part is configured to determine a required traction force corresponding to an output rotational speed based on a required traction force characteristic. A command torque determining part is configured to determine a command torque to be transmitted to a motor to obtain the required traction force. An opposite movement determining part is configured to determine that a vehicle is oppositely moving when a vehicle speed becomes a predetermined speed threshold or greater in a direction opposite to a moving direction corresponding to a position of a forward/rearward movement operating member. A traction force assisting part is configured to perform a traction force assisting control when it is determined that the vehicle is oppositely moving. The traction force assisting part is configured to increase the required traction force in the moving direction corresponding to the position of the forward/rearward movement operating member.