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.

An electro-hydraulic park control system includes a park piston and a park control valve disposed in a valve body of a transmission of a vehicle and configured to control a supply of hydraulic fluid pressure to control the park piston and to operate such that (i) no single element failure of the transmission will cause the transmission to shift from a park state to a non-park state or (ii) to shift from a drive, reverse, or neutral state to the park state, (iii) the transmission is able to remain in the non-park state and remain in or transition to the neutral state when a controller of the transmission is malfunctioning while the transmission is operating in the drive, reverse, and neutral states, and (iv) the transmission is able to quickly transition to the park state while an engine/motor driven pump of the transmission is off or not running.

A parking lock includes a locking pawl (2) and an interlocking element (6) arranged on a connecting bar (5) to a selector lever (4). The end of the connecting bar (5) facing away from the interlocking element (6) is articulatedly connected to the selector lever (4). A hydraulically actuatable actuator (10) includes two pistons (11, 12) provided for disengaging the parking lock. During normal operation, a detent device (13), which is actuatable by an electromagnet (13a), locks the first piston (11) in a piston position corresponding to an engaged condition (P_ein) or a disengaged condition (P_aus). Without requiring activating the electromagnet (13a) to release the detent device (13), the parking lock, during normal operation, is manually disengagable with an emergency disengagement device (15) acting upon the second piston (12) and is manually engagable with an emergency engagement device (16) acting upon the detent device (13).

A parking lock system for a motor vehicle includes a parking lock housing mountable on a transmission housing. A pawl is mounted on the parking lock housing so as to be rotatable about an axis of rotation. A switching rod is mounted on the parking lock housing so as to be slidable in an actuation direction. An actuation element is mounted on the switching rod. The axis of rotation is arranged parallel to the actuation direction.

A transmission for an agricultural or heavy load vehicle is provided, and includes a central drive shaft, at least one planetary gearset comprising a planet carrier, at least one output drive element, and one brake device. The drive shaft is connected to the output drive element via the planetary gearset. The brake device is located between the planet carrier and the output drive element in the form of a ring gear, such that the output drive element can be coupled to the planet carrier via the brake device.

A transmission for a vehicle. The transmission includes a housing and a valve block arranged in the housing, and a parking lock mechanism. The parking lock mechanism has a wheel rotationally locked to a shaft of the transmission, a pawl and a hydraulic actuator arranged for engagement of the wheel and the pawl for locking the shaft. The actuator is hydraulically connected to the valve block such that the actuator is supplied by hydraulic fluid from the valve block.

A hydraulic transaxle facilitates mounting a parking brake unit which requires no link mechanism and is compact. The parking brake unit includes a brake rotor provided on a rotation shaft and a locking member being displaceable between a first position where the brake rotor is locked and a second position where the brake rotor is unlocked. The locking member includes a locking portion which is engaged in a recess formed in the brake rotor that locks the brake rotor in the first position, and a non-locking portion which is placed at a position corresponding to the recess and which separates from the brake rotor in the second position. The hydraulic transaxle further includes an oil-supply mechanism capable of displacing the locking member to the second position.

A parking apparatus for a vehicle may include: a piston moved according to whether hydraulic pressure is introduced; a detent lever rotated by the movement of the piston; a sprag disposed on a rotation path of the detent lever, and locked to the detent lever so as to restrict the rotation of the detent lever; and a driver contacted with the sprag, and configured to transfer rotational power to the sprag.

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.

The invention relates to a hydraulic system for a vehicle transmission, comprising: a hydraulic circuit arranged for generating a pressure, a hydraulic actuator arranged for engaging a park lock system, wherein the hydraulic actuator is hydraulically connected to the hydraulic circuit for actuation of the hydraulic actuator using the pressure, and a back-up system configured to keep he pressure above a predetermined pressure threshold for maintaining an actuation of the hydraulic actuator for a predetermined period of time in case of an operational interruption of a transmission control unit of the vehicle.