A hydrodynamic friction clutch may include a rotatably mounted shaft, a drive disc non-rotatably fixed on the shaft, and an output body rotatably fixed on the shaft. The drive disc may include a radially extending annular transmission region for receiving a viscous fluid and via which the drive disc may be couplable to the output body for transmitting a torque, and an annular segment-shaped storage chamber for receiving the viscous fluid. The transmission region may be fluidically connected to the storage chamber via an inlet path and a drainage path. In the inlet path, a closable valve opening for controlling the quantity of the viscous fluid in the transmission region may be provided. The inlet path may include an annular segment-shaped communication passage, which may fluidically connect the storage chamber to the valve opening. The drainage path may fluidically connect to the inlet path at the valve opening.

A vehicle transmission includes a hydraulic circuit and a control unit. The control unit is configured to: obtain (20) a target pressure specification; convert (26) the target pressure specification into a target volume flow rate; determine (42) a valve volume flow rate as a function of the target volume flow rate and as a function of parameters that represent system properties of the hydraulic circuit; determine (46) a pressure drop at a valve due to flow forces as a function of the valve volume flow rate; determine (48) a compensated valve output pressure as a function of the valve volume flow rate and the pressure drop; determine (58) the electric control current as a function of the compensated valve output pressure; and activate a valve with the electric control current.

A pressure control valve (1) includes a pressure port (P), a consumer port (A), a tank port (T), and a piston (K) which is displaceable counter to the force of a first spring (F1) and a second spring (F2). The springs (F1, F2) and area ratios of the pressure control valve (1) are designed such that the pressure port (P), in the non-pressurized condition, is connected to the consumer port (A) via an opening cross-section of the pressure control valve (1). An opening cross-section between the pressure port (P) and the consumer port (A) decreases depending on the pressure at the consumer port (A), and, upon attainment of a limiting pressure at the consumer port (A), the consumer port (A) is connected to the tank port (T). A related hydraulic system (HY) and a related motor vehicle transmission (G) are also provided.

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.

A method for controlling power takeoff (PTO) clutch engagement includes determining an output clutch speed, adjusting a clutch current at a predetermined rate, estimating an inertial load of a PTO implement and adjusting the clutch current for one or more times at a time interval, and selecting a clutch control algorithm configured for the inertial load of the PTO implement.

According to one embodiment, a current detection circuit (12) includes: a detection resistor (Rs) provided between a solenoid valve (106) and a solenoid driver (11); an amplification unit (121) configured to amplify a detected voltage of the detection resistor (Rs); an AD converter (122) that is driven by a reference voltage (Vref) generated based on a reference current (Iref) and configured to convert an output voltage from the amplification unit (121) into a digital value and output the digital value as a detected current value (D1); and a correction unit configured to perform a correction on the detected current value (D1). The correction unit includes: a temperature sensor (123); a storage unit (125) configured to store information about temperature characteristics of the detected current value (D1) generated due to temperature characteristics of a reference current in each of two or more different temperature regions; and an operation unit configured to apply, to the detected current value (D1), a first correction coefficient calculated based on a detection result of the temperature sensor (123) and information about temperature characteristics of the detected current value (D1) stored in the storage unit (125).

An AWD-vehicle control device includes a transfer clutch that adjusts a driving force, a detector that detects a steering angle of a steering wheel, a detector that detects an accelerator pedal opening, a detector that detects a vehicle speed, a detector that detects an engine revolution speed, a detector that detects a turbine revolution speed of a torque converter, and a transfer clutch controller that adjusts hydraulic pressure supplied to the transfer clutch and controls a coupling force of the transfer clutch. If a predetermined period has passed from the accelerator pedal opening becoming less than a predetermined opening, the vehicle speed is within a predetermined range, a deviation between the engine and turbine revolution speeds is less than a predetermined speed, and the steering angle is equal to a first predetermined angle or greater, the transfer clutch controller controls the hydraulic pressure to reduce the coupling force.

A method for controlling PTO clutch engagement includes determining a first change in clutch speed based on an inertial load of a PTO implement. The method also includes determining a second change in clutch speed based on a threshold amount of energy of a PTO clutch. The method further includes determining a third change in clutch speed between the first change in clutch speed and the second change in clutch speed. The method also includes adjusting a clutch current based on the third change in clutch speed.

A dual clutch device is provided with a first piston for engaging a first clutch by using hydraulic pressure supplied to a first hydraulic chamber and disengaging the first clutch by using a first spring, a second piston for engaging a second clutch by using hydraulic pressure supplied to a second hydraulic chamber and disengaging the second clutch by using a second spring, first supply lines for supplying hydraulic pressure to the first hydraulic chamber and a second hydraulic canceling chamber, second supply lines for supplying hydraulic pressure to the second hydraulic chamber and a first hydraulic canceling chamber, a first valve for allowing or blocking the hydraulic pressure supply to the first hydraulic chamber and the second hydraulic canceling chamber, and a second valve for allowing or blocking the hydraulic pressure supply to the second hydraulic chamber and the first hydraulic canceling chamber.

An agricultural vehicle includes an engine, a transmission driven by the engine, and a controller. The controller, in operation, adjusts a gear ratio of the transmission using an algorithm. The algorithm, in operation, performs the following steps: reduce a torque capacity of a first offgoing clutch of the transmission to a first torque target, reduce the torque capacity of the first offgoing clutch to a second torque target while adjusting the torque capacity of a first oncoming clutch of the transmission to a third torque target, such that the gear ratio of the transmission is modified in a first direction, and increase the torque capacity of the first oncoming clutch to a desired torque capacity.