A lubrication system for a power transmission unit that supplies oil to a starting clutch in an appropriate amount irrespective of an engagement state of the starting clutch. When the friction clutch is completely engaged or disengaged, a first control valve is brought into a low inflow rate mode, and the second control valve is brought into a low outflow rate mode. When the friction clutch is engaged while causing a slip the first control valve is brought into a high inflow rate mode, and the second control valve is brought a high outflow rate mode.

Proposed is a system for operating and lubricating a clutch of a work vehicle. The system includes a forward-backward switching clutch portion connected to a first transmission hydraulic line, a main transmission clutch portion connected to the first transmission hydraulic line so as to be disposed in parallel with the forward-backward switching clutch portion, an auxiliary transmission clutch portion connected to a second transmission hydraulic line disposed in parallel with the first transmission hydraulic line, and a lubricating oil supply portion configured to supply oil as a lubricant to each clutch friction element. The lubricating oil supply portion includes a clutch lubrication valve unit, and is configured to always allow oil supply to the clutch friction elements of each of the main transmission clutch portion and the auxiliary transmission clutch portion, and is configured to intermittently allow oil supply to the clutch friction element of the forward-backward switching clutch portion.

The present disclosure provides an oil pressure supply system of an automatic transmission for a vehicle. The system may include: a mechanical oil pump; a line regulator valve configured to stably control the oil pressure supplied through the line pressure path and to supply the oil pressure to a first path; a torque converter control valve configured to control the oil pressure supplied through the first path and to supply the oil pressure to a second path and a third path; a torque converter lockup clutch control valve; an electric oil pump; a switch valve disposed on the seventh path and configured to open and close the oil pressure supplied to an eighth path; and a flow control valve configured to control a portion of the oil pressure supplied to the eighth path and to supply the portion of the oil pressure to the cooling/lubricating unit through a ninth path.

A first valve is disposed in an oil passage through which the engaging pressure generated by a linear solenoid valve is supplied to A second brake. The first valve is closed when the second brake is released, so as to close the oil passage, and is opened when the second brake is engaged, so as to open the oil passage. A second valve is disposed in a lubricating oil passage through which lubricating oil is supplied to the second brake, and communicates with the linear solenoid valve. The second valve is opened when the engaging pressure is supplied from the linear solenoid valve, so as to open the lubricating oil passage, and is closed when no engaging pressure is generated by the linear solenoid valve.

A bulldozer includes a steering clutch, a steering brake, a hydraulic pump that discharges a lubricating oil, a first lubricating oil supply path, a second lubricating oil supply path, a third lubricating oil supply path, and a flow amount switching valve disposed on the second lubricating oil supply path. The first lubricating oil supply path supplies a portion of the lubricating oil discharged by the hydraulic pump to the steering clutch The second lubricating oil supply path supplies a portion of the lubricating oil discharged by the hydraulic pump to the steering brake. The third lubricating oil supply path supplies, to the steering brake, a portion of the lubricating oil that has passed through the steering clutch. The flow amount switching valve switches an amount of the lubricating oil supplied to the steering brake.

A clutch assembly comprises at least one controllable friction clutch for variable torque transmission between a clutch input part and a clutch output part; a hydraulic actuator assembly for actuating the friction clutch, the actuator assembly comprising a hydraulic pump, a hydraulic chamber in which hydraulic pressure for the friction clutch is built up by the hydraulic pump and a return flow element with an orifice, via which hydraulic fluid can flow out of the hydraulic chamber into a housing reservoir when the hydraulic pump is not actuated, wherein the hydraulic fluid defines a filling level in the housing reservoir; wherein an outlet opening of the return flow element lies below the filling level of the hydraulic fluid in a inactive state.

The present disclosure provides an oil pressure supply system of an automatic transmission for a vehicle. The system may include: a mechanical oil pump; a line regulator valve configured to stably control the oil pressure supplied through the line pressure path and to supply the oil pressure to a first path; a torque converter control valve configured to control the oil pressure supplied through the first path and to supply the oil pressure to a second path and a third path; a torque converter lockup clutch control valve; an electric oil pump; a switch valve disposed on the seventh path and configured to open and close the oil pressure supplied to an eighth path; and a flow control valve configured to control a portion of the oil pressure supplied to the eighth path and to supply the portion of the oil pressure to the cooling/lubricating unit through a ninth path.

A hydraulic component includes a piston and a cylinder with a piston receiving space in which the piston is displaceably arranged while defining a chamber, via which a pressure may be applied to a first end face of the piston, from a control chamber, via which pressure may be applied to a second end face of the piston which faces away from the first end face. A first hydraulic line and a second hydraulic line open into the chamber and a control line, which branches off from the first hydraulic line, opens into the control chamber. Due to the respective pressure ratio between the pressure in the chamber and the control chamber, the piston is displaceable from a closed position, in which the first and second hydraulic lines are fluidly decoupled, into an open position, in which the first and second hydraulic lines are fluidly connected, and vice versa.

A rear axle drive (2) for an AWD vehicle is presented. The rear axle drive (2) is connected to an hydraulic AWD coupling (3), wherein the rear axle drive (2) comprises a lubrication valve (4) for controlling the level of lubricant in at least one lubricant reservoir (6, 7) of the rear axle drive (2) for providing lubricant to gears and/or bearings of the rear axle drive (2). The lubrication valve (4) is functionally connected to a shut-off valve (5) of the AWD coupling (3) and the lubrication valve (4) of the rear axle drive (3) is controlled by movement of an actuating member (51, 54) of the AWD coupling (3).

The present disclosure relates to a duct valve for a clutch assembly of an off-road vehicle. The duct valve is configured to be coupled to a housing of the clutch assembly. The duct valve comprises a first duct attached to the housing and a first valve cage attached to the first duct. The first valve cage is configured to hold a first floatable element therewithin. The first floatable element is configured to have a first buoyancy and is configured to displace towards a first air opening of the first duct corresponding to a level of a liquid to seal the first air opening.