Methods and systems for hydraulic vehicle suspension are provided. A hydraulic suspension system, in one example, includes a first manifold including a piston-side interface and a rod-side interface fluidically coupled to a piston chamber and a rod chamber, respectively, for each of a first hydraulic cylinder and a second hydraulic cylinder. In the system, the first manifold includes a first electrically activated valve fluidically coupled to the piston-side interfaces, a first damping device, and a second damping device, the first electrically activated valve is configured to lock and unlock vertical motion of the first and second hydraulic cylinders and, while vertical motion of the first and second hydraulic cylinders is locked, the first electrically activated valve permits fluidic communication between the first and second hydraulic cylinders to permit free roll motion in the hydraulic suspension system.

A hydraulic level-adjustment device has a reservoir, a reversible hydraulic unit with a hydraulic pump, and a single-acting hydraulic linear actuator. To lift a vehicle chassis, the working space of the linear actuator can be pressurized by the hydraulic pump operated in its first pumping direction via its first pump connection and a fill line with a fill-check valve arranged therein. To lower the chassis, via its second pump connection, the hydraulic pump, operated in the reverse pumping direction, pumps hydraulic fluid into the reservoir via an outflow line with a throttle unit arranged therein. The pressure present upstream of the throttle unit acts on the control connection of a lockable, drainage-check valve via a control line and opens same, so that, under the weight of the motor vehicle, hydraulic fluid is forced out of the working space of the hydraulic linear actuator into the reservoir via the drainage line.

A hydraulic level-adjustment device has a reservoir, a reversible hydraulic unit with a hydraulic pump, and a single-acting hydraulic linear actuator. To lift a vehicle chassis, the working space of the linear actuator can be pressurized by the hydraulic pump operated in its first pumping direction via its first pump connection and a fill line with a fill-check valve arranged therein. To lower the chassis, via its second pump connection, the hydraulic pump, operated in the reverse pumping direction, pumps hydraulic fluid into the reservoir via an outflow line with a throttle unit arranged therein. The pressure present upstream of the throttle unit acts on the control connection of a lockable, drainage-check valve via a control line and opens same, so that, under the weight of the motor vehicle, hydraulic fluid is forced out of the working space of the hydraulic linear actuator into the reservoir via the drainage line.

A suspension device includes an actuator device provided with an extensible/contractible actuator body interposed between a sprung member and an unsprung member of a vehicle, a pump that supplies fluid to the actuator body to extend or contract the actuator body, and a controller that controls a rotation number of the pump. The controller has a road surface state index obtainment unit that obtains a road surface state index and a target rotation number determination unit that determines a target rotation number of the pump on the basis of the road surface state index.

A suspension device includes an actuator device provided with an extensible/contractible actuator body interposed between a sprung member and an unsprung member of a vehicle, a pump that supplies fluid to the actuator body to extend or contract the actuator body, and a controller that controls a rotation number of the pump. The controller has a road surface state index obtainment unit that obtains a road surface state index and a target rotation number determination unit that determines a target rotation number of the pump on the basis of the road surface state index.

An air management system for a vehicle. The air management system includes at least one air spring. A compressor is provided for filling the air spring. A central air line is fluidly connected to the air spring and the compressor. At least one spring air line extends between the central air line and the air spring. At least one suspension valve is disposed along the spring air line. At least one auxiliary air line extends between the spring air line and the central air line. At least one high flow exhaust valve is disposed along the auxiliary air line. At least one isolation check valve is disposed in series with the high flow exhaust along the spring air line. The isolation check valve allows air to pass through therethrough from the air spring to the central air line while preventing air from passing therethrough from the central air line to the air spring.

An air management system for a vehicle. The air management system includes at least one air spring. A compressor is provided for filling the air spring. A central air line is fluidly connected to the air spring and the compressor. At least one spring air line extends between the central air line and the air spring. At least one suspension valve is disposed along the spring air line. At least one auxiliary air line extends between the spring air line and the central air line. At least one high flow exhaust valve is disposed along the auxiliary air line. At least one isolation check valve is disposed in series with the high flow exhaust along the spring air line. The isolation check valve allows air to pass through therethrough from the air spring to the central air line while preventing air from passing therethrough from the central air line to the air spring.

A vehicle height adjustment apparatus includes: vehicle height adjustment units respectively provided to correspond to wheels of a vehicle body, and adjusting a vehicle height in response to the supply and discharge of a working fluid; a pressure tank storing the working fluid; a compressor pressure-feeding the working fluid; a valve body block formed by opening and closing valves, and interposed between the pressure tank and the compressor, and the vehicle height adjustment units; and a control unit adjusting a vehicle height by controlling the valve body block, wherein the valve body block is connected to the pressure tank, and working fluid outlet and inlet of the compressor, and upon the completion of the pressure feed of the working fluid, the control unit controls such that the working fluid outlet and inlet are communicated with each other.

A plurality of traveling wheels are supported via expandable/contractible tubular support members to a vehicle body frame. A hydraulic operation type vehicle height adjustment mechanism provided for each one of the traveling wheels, the vehicle height adjustment mechanism being capable of switching a relative height of the traveling wheel relative to the vehicle body frame within a predetermined length range by expanding/contracting the support member by a hydraulic cylinder. There are provided a hydraulic control valve capable of controlling feeding state of work oil to each one of the plurality of hydraulic cylinders, a controlling section for controlling an operation of the hydraulic control valve to bring the vehicle body to a target state via vehicle height adjustment by the hydraulic cylinder in response to a change in the posture of the vehicle body and a plurality of accumulators connected oil chambers of the respective plurality of hydraulic cylinders.

A method for pivoting a travel unit on a machine frame of a road milling machine between an outer end position and an inner end position offset toward a center of the machine relative to the outer end position, the road milling machine having a travel mechanism with multiple travel units, of which at least one travel unit is height-adjustable via a lifting column, comprising the steps of positioning a support foot mounted on the machine frame in a ground contact position to support the machine frame, lifting the travel unit, pivoting the travel unit between the outer end position and the inner end position, lowering the travel unit, and positioning the support foot in a stowed position.