A hydraulic control system for a multiple speed motor vehicle automatic transmission having electronic transmission range selection (ETRS) provides both a forward gear ratio and Park options during default conditions where the transmission loses electronic control when the ETRS system is in a drive mode. The hydraulic control system includes a two position default disable solenoid valve, an ETRS valve, a park servo, position sensors, a default disable valve, a drive select valve, various orifices and blow-off valves as well as main and auxiliary pumps, a torque converter, a torque converter regulator and control valve and a plurality of linear force solenoid valves and clutch regulation valves which control a like plurality of clutch and brake actuators.

A power transmission device includes a torque converter device, a first hydraulic pump, a first oil channel, a second oil channel, a third oil channel, a second pressure control valve, and a controller. The torque converter device has a torque converter and a lock-up clutch. The first oil channel supplies hydraulic fluid from the first hydraulic pump to the torque converter. The second oil channel drains hydraulic fluid from the torque converter. The third oil channel communicates with the first oil channel and the second oil channel. The second pressure control valve is disposed in the third oil channel. The controller sets the second pressure control valve to an open state when the lock-up clutch is in an engaged state.

The present disclosure describes a hydraulic control system comprising a first pressure chamber and a second pressure chamber, each pressure chamber configured to receive a hydraulic fluid, a first movable member configured to assume a position depending on a hydraulic pressure of the hydraulic fluid in the first pressure chamber and a second movable member configured to assume a position depending on a hydraulic pressure of the hydraulic fluid in the second pressure chamber, a hydraulic command circuit configured to provide the hydraulic fluid and to control the hydraulic pressure of the hydraulic fluid in the first pressure chamber and/or the second pressure chamber, having a switchable valve in fluid communication with the first pressure chamber, wherein the switchable valve is configured to be pilotable depending on the hydraulic pressure of the hydraulic fluid in the second pressure chamber.

A hydraulic system for a vehicle transmission with at least two friction elements, the system comprising a first hydraulic circuit comprising a pump for supplying hydraulic fluid to the first hydraulic circuit. A flow restriction may be provided in the first hydraulic circuit between an output of the pump and a sump for providing leakage of hydraulic fluid into the sump. Further, a second hydraulic circuit comprising a second pump may be arranged, wherein the hydraulic pressure in the first circuit is higher compared to the second circuit. A flow control element operated using hydraulic pressure from the first circuit may be arranged for controlling flow/pressure in the second circuit. Further, the hydraulic system may be arranged for generating a line pressure, wherein an actuator for engaging a park lock system may be connected to the first hydraulic circuit for enabling direct actuation by means of the line pressure.

Provided is a control device for a continuously variable transmission, which is capable of effectively preventing occurrence of surge pressure due to a stroke of a driven pulley being stopped by abutment. The control device for the continuously variable transmission includes a pressure regulating valve regulating an oil pressure of oil supplied from an oil supply source to a cylinder chamber of the driven pulley, a control valve controlling the pressure regulating valve, and a control part controlling the control valve. If the control part determines that a gear ratio of the continuously variable transmission is maximum, as a first condition, when an instructed oil pressure of the control valve for the pressure regulating valve is larger than an oil pressure of oil supplied from the pressure regulating valve to the driven pulley, a control for lowering the instructed oil pressure is performed.

The present disclosure describes a hydraulic control system comprising a first pressure chamber and a second pressure chamber, each pressure chamber configured to receive a hydraulic fluid, a first movable member configured to assume a position depending on a hydraulic pressure of the hydraulic fluid in the first pressure chamber and a second movable member configured to assume a position depending on a hydraulic pressure of the hydraulic fluid in the second pressure chamber, a hydraulic command circuit configured to provide the hydraulic fluid and to control the hydraulic pressure of the hydraulic fluid in the first pressure chamber and/or the second pressure chamber, having a switchable valve in fluid communication with the first pressure chamber, wherein the switchable valve is configured to be pilotable depending on the hydraulic pressure of the hydraulic fluid in the second pressure chamber.

A transmission includes a plurality of pneumatic actuators for gear shifting, wherein the pneumatic actuators are arranged to discharge compressed air via a common ventilation system including at least one ventilation opening arranged in a housing arrangement of the transmission. A method for controlling ventilation of the transmission includes determining that a predetermined flushing condition is fulfilled and, in response thereto, initiating a flushing action in which at least two of the pneumatic actuators are controlled to discharge compressed air simultaneously or substantially simultaneously to the common ventilation system so as to force air through the at least one ventilation opening.

Methods and systems for a transmission are provided herein. In one example, a hydraulic system is provided that includes a boost pump, a relief valve in fluidic communication with the boost pump and a reservoir, and a plurality of control valves in fluidic communication with the boost pump, positioned downstream of the relief valve, and in fluidic communication with a plurality of hydraulic devices. The hydraulic system further includes a controller designed to actively adjust a position of the relief valve based on an aggregate hydraulic pressure demand of the plurality of hydraulic devices to alter a boost pressure of a hydraulic fluid supplied to the plurality of control valves.

A transmission hydraulic control system includes a manual valve, a default valve, and a clutch prime valve. The manual valve allows fluid flow from a pressurized line to a drive line when the manual valve is open (when a transmission is in drive or reverse). The manual valve prevents fluid flow from the pressurized line to the drive line when the manual valve is closed (when the transmission is in neutral or park). The clutch prime valve allows fluid to flow from the pressurized line to the drive line, and thereby bypass the manual valve, when the manual valve is closed and the clutch prime valve is open. The default valve allows fluid bypassing the manual valve to flow to prime a clutch of the transmission when the default valve is open. The clutch prime valve prevents fluid from bypassing the manual valve when the clutch prime valve is closed.

A drive unit includes a motor, a torque converter, a torque transmission member, first and second transmission paths, first and second gear trains, and a controller. The torque converter amplifies torque directed in a first direction. The first transmission path transmits torque through the torque converter. The second transmission path transmits torque without through the torque converter. The first gear train outputs torque directed in the first direction as forward torque. The second gear train outputs torque directed in the first direction as reverse torque. The controller executes a first forward moving mode such that the motor is rotated in the first direction, and torque is outputted through the first transmission path and the first gear train. The controller executes a second forward moving mode such that the motor is rotated in a second direction, and torque is outputted through the second transmission path and the second gear train.