A suspension device includes: a damper that has an extension-side chamber and a contraction-side chamber; an extension-side passage connected to the extension-side chamber; a contraction-side passage connected to the contraction-side chamber; a switching device that connects one of the extension-side passage and the contraction-side passage to the supply passage and connecting the other of the extension-side passage and the contraction-side passage to the discharge passage selectively; an extension-side damping element provided in the extension-side passage; a contraction-side damping element provided in the contraction-side passage; a control valve capable of adjusting a pressure in the supply passage; an intake check valve provided midway in the intake passage; and a supply-side check valve provided in the supply passage between the control valve and the pump.

To improve off-road travel performance, ECU is configured to: set one of front left and right wheels and rear left and right wheels as roll stiffness decrease subject wheels and set another as non-roll stiffness decrease subject wheels; bring a spring switching valve and a leveling valve into an open state for each of the roll stiffness decrease subject wheels, causing left and right hydraulic cylinders to communicate to each other for the roll stiffness decrease subject wheels; and bring the spring switching valve and the leveling valve into a closed state and bring a bypass valve into the open state for one of the left and right wheels of the non-roll stiffness decrease subject wheels, to cause a second gas spring for one of the left and right wheels of the non-roll stiffness decrease subject wheels to communicate to the hydraulic cylinders of the roll stiffness decrease subject wheels.

To improve off-road travel performance, ECU is configured to: set one of front left and right wheels and rear left and right wheels as roll stiffness decrease subject wheels and set another as non-roll stiffness decrease subject wheels; bring a spring switching valve and a leveling valve into an open state for each of the roll stiffness decrease subject wheels, causing left and right hydraulic cylinders to communicate to each other for the roll stiffness decrease subject wheels; and bring the spring switching valve and the leveling valve into a closed state and bring a bypass valve into the open state for one of the left and right wheels of the non-roll stiffness decrease subject wheels, to cause a second gas spring for one of the left and right wheels of the non-roll stiffness decrease subject wheels to communicate to the hydraulic cylinders of the roll stiffness decrease subject wheels.

Methods and systems for vehicle suspension are provided. A leveling manifold includes, in one example, a plurality of electrically-activated valves arranged between, on a first end, a rod-side and a piston-side of one or more hydraulic cylinders, and on a second end, a pressure source and a tank, wherein the plurality of electrically-activated valves include a first valve, a second valve, a third valve, and a fourth valve. The leveling manifold further includes a first flow path extending through the first and second valves and from the rod-side to the second end and a second flow path extending through the third and fourth valves and from the piston-side to the second end, the leveling manifold is designed to manage operation of the first, second, third, and/or fourth valves to independently adjust a position and a stiffness of the one or more hydraulic cylinders.

Methods and systems for vehicle suspension are provided. A leveling manifold includes, in one example, a plurality of electrically-activated valves arranged between, on a first end, a rod-side and a piston-side of one or more hydraulic cylinders, and on a second end, a pressure source and a tank, wherein the plurality of electrically-activated valves include a first valve, a second valve, a third valve, and a fourth valve. The leveling manifold further includes a first flow path extending through the first and second valves and from the rod-side to the second end and a second flow path extending through the third and fourth valves and from the piston-side to the second end, the leveling manifold is designed to manage operation of the first, second, third, and/or fourth valves to independently adjust a position and a stiffness of the one or more hydraulic cylinders.

A vehicle height adjustment apparatus includes a control device. The control device controls the opening degree of the solenoid valve to allow a movement amount of the support member to reach a movement amount target value that corresponds to the vehicle height set in advance, in accordance with the weight applied to the vehicle. The control device controls the opening degree of the solenoid valve to change the movement amount of the support member based on a difference between a value based on the information related to the vehicle height and a vehicle height-related target value, on condition that the movement amount of the support member reaches the movement amount target value and the value based on the information related to the vehicle height obtained by the information obtaining device does not reach the vehicle height-related target value that corresponds to the vehicle height set in advance.

A vehicle-height control system includes: a fluid supply and discharge device including a compressor device and a tank storing fluid pressurized by the compressor device; a vehicle-height control actuator corresponding to a wheel and connected to the fluid supply and discharge device; a vehicle height controller that controls a vehicle height for the wheel by controlling the fluid supply and discharge device to control supply and discharge of fluid to and from the vehicle-height control actuator; a tank pressure controller that controls a tank pressure; and a fluid supply controller that supplies the fluid to a low pressure portion by controlling the fluid supply and discharge device at start and/or termination of at least one of control executed by the vehicle height controller and control executed by the tank pressure controller. The low pressure portion is at least a portion of the fluid supply and discharge device.

An air spring for a heavy-duty vehicle includes a bellows chamber, a piston chamber, and at least one opening. The piston chamber is operatively connected to the bellows chamber. The at least one opening is in fluid communication with the bellows chamber and the piston chamber to provide fluid communication between the bellows chamber and the piston chamber. An orifice assembly is disposed adjacent the at least one opening for variably changing the size of the opening. The air spring provides damping to the heavy-duty vehicle.

Methods and systems for vehicle suspension are provided. A leveling manifold includes, in one example, a plurality of electrically-activated valves arranged between, on a first end, a rod-side and a piston-side of one or more hydraulic cylinders, and on a second end, a pressure source and a tank, wherein the plurality of electrically-activated valves include a first valve, a second valve, a third valve, and a fourth valve. The leveling manifold further includes a first flow path extending through the first and second valves and from the rod-side to the second end and a second flow path extending through the third and fourth valves and from the piston-side to the second end, the leveling manifold is designed to manage operation of the first, second, third, and/or fourth valves to independently adjust a position and a stiffness of the one or more hydraulic cylinders.

Methods and systems for vehicle suspension are provided. A leveling manifold includes, in one example, a plurality of electrically-activated valves arranged between, on a first end, a rod-side and a piston-side of one or more hydraulic cylinders, and on a second end, a pressure source and a tank, wherein the plurality of electrically-activated valves include a first valve, a second valve, a third valve, and a fourth valve. The leveling manifold further includes a first flow path extending through the first and second valves and from the rod-side to the second end and a second flow path extending through the third and fourth valves and from the piston-side to the second end, the leveling manifold is designed to manage operation of the first, second, third, and/or fourth valves to independently adjust a position and a stiffness of the one or more hydraulic cylinders.