A motor grader having ride control for dampening machine bounce using a DCM assembly rotatably coupled to and suspended from a frame of the motor grader is disclosed. Each lift cylinder for the DCM may have an associated ride control circuit with an accumulator, a ride control conduit fluidly connected to a carry end of the lift cylinder and having a flow restriction element, and a ride control accumulator valve fluidly connected to the accumulator and the ride control conduit and operable to either block or allow fluid communication between the carry end and the accumulator through the flow restriction element. Each rid control circuit may also include a head end valve fluidly connected to between the head end of the lift cylinder and a low pressure fluid reservoir and operable to block or allow fluid communication between the head end and the low pressure fluid reservoir.

A power system for a working machine, including a prime mover drivingly connectable to a main shaft; a planetary gear set including a rotatable first member drivingly connected to the main shaft, a rotatable second member and a rotatable third member for propulsion of the working machine; a hydraulic system including at least one hydraulic actuator for performing a working function of the working machine; an electric energy storage system; a first hydraulic machine mechanically coupled to the main shaft and hydraulically coupled to the hydraulic system; a first electric machine mechanically coupled to the main shaft; a second electric machine mechanically coupled to the rotatable second member, wherein the electric energy storage system is electrically connected to the first and second electric machines, and wherein the power system further includes a second hydraulic machine mechanically coupled to the rotatable second member and hydraulically coupled to the hydraulic system.

Provided is a hydraulic machine. A pump pressurizes fluid using power provided by a power source. An actuator works using the pressurized fluid from the pump. A recovery part recovers energy from fluid discharged from the actuator. A first operator input device receives a desired input from an operator to select an eco-mode or a boost mode. The recovery part includes an accumulator storing hydraulic energy by receiving the fluid discharged from the actuator and an assist unit assisting the power source using the hydraulic energy stored in the accumulator. The controller controls the pump such that output power of the pump does not exceed Plmax when the eco-mode is selected or the assist unit does not assist the power source and that the output power does not exceed P2max when the boost mode is selected and the assist unit assists the power source, where Plmax < P2max.

A hydraulic system includes a first and a second rotating hydraulic machine, the first and second hydraulic machine being arranged to provide a torque via a common output shaft; a first valve arrangement for providing a differential hydraulic pressure level over the first hydraulic machine by using two sources of hydraulic fluid having different hydraulic pressure levels, a second valve arrangement for providing a differential hydraulic pressure level over the second hydraulic machine by using two sources of hydraulic fluid having different hydraulic pressure levels; and a control unit configured to control the first valve arrangement and the second valve arrangement such that different discrete levels of torque are provided via the output shaft of the hydraulic system. A hydraulic system for providing different discrete levels of torque using one hydraulic machine and a plurality of differential pressure levels, and a method for controlling a hydraulic system, are also provided.

Device for recovering hydraulic energy in a machine comprising at least a first differential cylinder-piston assembly having a differential cylinder with a separate rod and base side, at least a second differential cylinder-piston assembly having a differential cylinder with a separate rod and base side, and at least one hydraulic accumulator that can be hydraulically connected to at least one of the differential cylinder-piston assemblies, wherein the differential cylinder-piston assemblies are mechanically coupled to one another, and wherein the potential energy of at least one of the differential cylinder-piston assemblies retracting under a compressive load can at least partially be stored in the hydraulic accumulator.

There is provided a driving device for a work machine, having a closed hydraulic circuit system for driving cylinders with hydraulic pumps, the driving device making the speed of operation substantially the same in both directions of piston rod extension and contraction. The driving device includes: a first hydraulic pump that has flow rate control device for controlling the flow rate and direction of hydraulic fluid to be delivered; a single rod hydraulic cylinder that is driven with the hydraulic fluid to drive one of work members of a work device on the work machine; a closed hydraulic circuit that connects the first hydraulic pump with the single rod hydraulic cylinder to form a closed circuit using flow lines through which the hydraulic fluid flows; a branch line that branches from the flow line between the first hydraulic pump and the single rod hydraulic cylinder; a first flow line of which one end is connected to the branch line; a tank to which the other end of the first flow line is connected; and a hydraulic fluid flow rate control device attached to the first flow line to control the flow rate of the hydraulic fluid flowing from the branch line to the tank or from the tank to the branch line.

A drive control system includes an electric motor, a capacitor, a revolution sensor, a driving device, and a control device. The driving device causes the capacitor to supply electric power to the electric motor to operate the electric motor and causes the capacitor to store the electric power, generated by the electric motor, to brake a turning body. The driving device configured as above is driven by driving electric power supplied from the capacitor. When a charging stop condition is satisfied, the control device stops the driving electric power supplied from the capacitor to the driving device. The charging stop condition is a condition that a turning speed detected by the revolution sensor is a predetermined speed or less while the turning body is decelerating.

A ride control valve includes a valve housing (30) having a main spool (32) longitudinally displaceably arranged in the valve housing, a balance spool (34), and fluid passage points for a pressure supply (P), a tank return line (T), an accumulator (14) and a boom cylinder unit (10). The balance spool (34) continuously balances the pressure between the fluid ports of the accumulator (14) and the boom cylinder unit (10). The main spool (32) is controlled by the operator and initially interconnects these fluid ports of the accumulator (14) and the boom cylinder unit (10), starting from a closed fluid connection, via a restricted fluid connection, to a fully opened fluid connection, or disconnects them from each other in reverse sequence.

A hydraulic excavator drive system includes: a first pump connected to a head-side chamber of a boom cylinder; and a second pump that supplies hydraulic oil to one of, or both, an arm cylinder and a bucket cylinder. The first pump is driven by an electric motor. The drive system further includes a switching valve that is in a first position at a boom raising operation and in a second position at a vehicle body lifting operation. The first position is a position in which the switching valve brings a rod-side chamber of the boom cylinder into communication with a tank, and the second position is a position in which the switching valve brings the rod-side chamber into communication with the second pump.

A control system for a construction machine includes: a boom cylinder; a boom switching valve; a fluid pressure motor adapted to drive a motor generator by being rotated by means of a return fluid guided from a piston side chamber; a regeneration control valve adapted to adjust a first supply amount serving as a supply amount of a working fluid supplied from the piston side chamber to the boom switching valve, and a second supply amount serving as a supply amount of the working fluid supplied from the piston side chamber to the fluid pressure motor; and a controller adapted to control the regeneration control valve so that the second supply amount becomes smaller than the first supply amount in a case where a stroke amount of a spool becomes an upper limit value or more.