A hydraulic system (1) for electro-hydraulically pressing and/or moving a first (8) and a second (9) set of disks of a CVT transmission (10) is provided. The hydraulic system (1) includes two electrically driven hydraulic pumps (4, 5). In order to reduce energy consumption during operation of the hydraulic system, the hydraulic pumps (4, 5) are in the form of self-inhibiting hydraulic pumps (4, 5) which, when a hydraulic pressure is applied and the associated electric drive is switched off, substantially maintain the applied hydraulic pressure as a result of a static friction and a residual moment of the associated electric drive.

A hydraulic system (1) of an automatic transmission of a motor vehicle includes a hydraulic pump (2) powered by a drive engine for supplying pressure to the hydraulic system (1). A hydraulic reservoir (10) by which, when the drive engine is at rest, a pressure drop in a main pressure circuit (7) of the hydraulic system (1) can at least be delayed. The hydraulic reservoir (10) is connected to the main pressure circuit (7) by way of an orifice (14) or a throttle.

The hydraulic circuitry of a factory installed automatic automotive transmission is modified to replace an underdrive accumulator spring with a shorter spring and a separate lower rated spring washer operatively associated with the shorter replacement underdrive accumulator spring. The combined replacement spring and spring washer conjointly act on an underdrive accumulator piston to move it in two predetermined distances, in two separate continuous stages, namely, movement of the piston for a first predetermined distance is controlled by the spring washer, while movement of the piston for a second predetermined distance is controlled by the replacement spring. The spring washer has a lower spring rating than the replacement spring, so that less fluid pressure is required to move the piston the total distance traveled, resulting in less fluid pressure applied to an underdrive clutch than in the factory installed transmission. The spring ratings of the replacement spring and the spring washer are selected such that the total fluid pressure required to move the piston both the first and second predetermined distances is less than the fluid pressure required to overcome the resilient force of underdrive piston return springs acting on an underdrive apply piston so that a lower fluid pressure is applied to an underdrive clutch.

A vehicle includes an engine, a transmission, and a controller. The transmission has clutches, a circuit configured to transport fluid to the clutches, a pump configured to circulate the fluid through the circuit, and an accumulator disposed along the circuit. The controller is programmed to, responsive to an engine start and a fluid temperature being less than a temperature threshold, discharge the accumulator to prime the pump.

Methods and systems for improving operation of a vehicle driveline that includes an engine and an automatic transmission with a torque converter are presented. In one non-limiting example, the engine may be stopped while a vehicle in which the engine operates is rolling. A transmission coupled to the engine may be shifted as the vehicle rolls so that vehicle response may be improved if a driver requests an increase of engine torque.

A transmission assembly including a clutch system, an accumulator, and a controller is provided. The clutch system may include a flow source. The accumulator may be selectively in communication with the flow source via a solenoid valve. The controller may be programmed to, responsive to detection of a vehicle stop and the accumulator charged below a predetermined threshold, output a command to open the solenoid valve to rapidly charge the accumulator from the flow source. The predetermined threshold may be an accumulator pressure between 700 kPa and 900 kPa. The controller may be further programmed to, responsive to detection of the accumulator being charged to or above the predetermined threshold, output a shut down command to an engine in communication with the transmission assembly and to output a close command to the solenoid valve. The flow source may be a pump out circuit or a line pressure circuit.

A hydraulic control system for a continuously variable transmission (CVT) includes a pressure regulator subsystem, a selection valve in downstream fluid communication with the pressure regulator subsystem, the selection valve configured to control a flow of pressurized oil from the pressure regulator subsystem to a primary pulley circuit and a secondary pulley circuit, the primary pulley circuit in fluid communication with a primary pulley and the secondary pulley circuit in communication with a secondary pulley, and a ratio control pump disposed in fluid communication between the primary pulley circuit and the secondary pulley circuit, wherein rotation of the ratio control pump in a first direction pumps pressurized oil from the secondary pulley circuit to the primary pulley circuit and rotation of the control pump in a second direction pumps pressurized oil from the primary pulley circuit to the secondary pulley circuit to change a ratio of the CVT.

A hydraulic circuit device for a vehicle, includes a clutch, a flow path, a fluid pump, a pressure generating device, and a control valve. The control valve is configured to determine whether a transmission start-stop function activation condition other than a vehicle speed is satisfied, determine whether a system start-stop function activation condition related to a component of the vehicle is satisfied, the component being other than the transmission, determine whether the vehicle speed is equal to or lower than a first speed threshold, and boost a line pressure of the flow path to accumulate pressure in the pressure generating device for preparing activation of the start-stop function if it is determined that the transmission start-stop function activation condition and the system start-stop function activation condition are satisfied, and if it is determined that the vehicle speed is equal to or lower than the first speed threshold.

A hydraulic system for an automatic transmission, in particular a dual-clutch transmission, of a motor vehicle. A high-pressure circuit, in which a pressure accumulator, at least one clutch, and gear selectors are connected, and a low-pressure circuit for cooling the clutch. The high-pressure circuit and the low-pressure circuit have at least one hydraulic pump, which can be driven by an electric motor. The hydraulic system also has a control unit, which activates the electric motor of the hydraulic pump when a requirement to charge the pressure accumulator is identified. The high-pressure and low-pressure circuits are connected via a bypass line to an integrated accumulator charging valve, which in a non-charging position fluidically connects the hydraulic pump to the low-pressure circuit and in a charging position fluidically connects the hydraulic pump to the high-pressure circuit.

Methods and systems for a hydromechanical transmission. In one example, a vehicle system includes a hydromechanical transmission with a power-take off (PTO) that is designed to rotationally couple to an implement. The vehicle system further includes an engine coupled to the hydromechanical transmission and a power-management control unit configured to, during a drive or coast condition, cause the power-management control unit to: determine a net available power for the hydromechanical transmission and manage a power flow between the hydromechanical transmission, a drive axle, and the implement based on the net available power.