A hydraulic system in a work machine includes a travel operation device provided in a pilot oil path between a hydraulic pump a travel pump and including an operation member and configured to generate a pilot pressure supplied via the pilot oil path and an additional pilot pressure in accordance with an operation amount of the operation member. The travel pump is to control a flow direction of hydraulic oil supplied to a travel motor based on the pilot pressure and the additional pilot pressure. A pressure selection valve is provided in a first coupling oil path to select a selected pressure from the pilot pressure and the additional pilot pressure to apply the selected pressure to the pilot hydraulic oil in the second coupling oil path. A pressure adjustment valve is provided in a second coupling oil path to control the selected pressure to be an adjusted pilot pressure.

A construction machine according to an exemplary embodiment of the present invention includes: an engine; a boom cylinder which is divided into a head side and a rod side; a regeneration line through which hydraulic fluid discharged from the head side of the boom cylinder moves when the boom descends; a regeneration motor which is connected with the regeneration line and is operated, and assists the engine; a pilot pump which generates a pilot pressure; a pilot line through which pilot hydraulic fluid discharged from the pilot pump moves; a regeneration connection line which connects the pilot line and the regeneration line; an on/off valve installed in the regeneration connection line; and a control device which closes the on/off valve when a pressure of the pilot line drops below a predetermined pressure or the hydraulic fluid discharged from the boom cylinder is supplied to the regeneration motor.

A control valve of hydraulic system for a working machine is provided, which includes a main body and a spool. The main body includes first, second, third, fourth and fifth ports, and first second, third, fourth and fifth inner fluid paths connected to the first, second, third, fourth and fifth ports, respectively. The spool is configured to move between a neutral position and a communicating position allowing fluid communication between the second inner fluid path and the fifth inner fluid path or between the first inner fluid path and the fifth inner fluid path. The spool includes a communicating hole configured to allow the fluid communication between the second port and the fourth port, or between the first port and the fourth port, when the spool is in a position between the communicating position and the neutral position.

Systems and apparatuses include a primary hydraulic pump including a primary displacement actuator and a primary pressure port, a primary load sense system fluidly coupled to the primary displacement actuator, a secondary hydraulic pump including a secondary displacement actuator and a secondary pressure port, a secondary load sense system fluidly coupled to the secondary displacement actuator, and a crossover pressure controller coupled between the primary pressure port and the secondary pressure port and including: a selectively energizable crossover pressure solenoid, and a crossover pressure spool movable by the crossover pressure solenoid between a combined pressure position providing fluid communication between the primary pressure port and the secondary pressure port, and a separate pressure position inhibiting fluid communication between the primary pressure port and the secondary pressure port.

A vehicle includes a chassis, an implement coupled to the chassis, a hydraulic actuator configured to move the implement relative to the chassis, a tractive element coupled to the chassis, a hydraulic motor configured to drive the tractive element to propel the vehicle, a drive pump fluidly coupled to the hydraulic motor, a charge pump coupled to the chassis and configured to provide a flow of pressurized fluid, and a valve assembly fluidly coupled to the charge pump. The valve assembly is configured to (a) direct a first portion of the flow of pressurized fluid to the drive pump and (b) selectively direct a second portion of the flow of pressurized fluid to the hydraulic actuator.

To make it possible to control supply, discharge, and recycled flow rates independently of each other for the boom cylinder in a construction machine comprising first and second boom spool valves respectively connected to first and second hydraulic pumps. When the boom cylinder is contracted, the first boom spool valve is configured to control the recycled flow rate from head side oil chamber to rod side oil chamber, the second boom spool valve is configured to control the discharge flow rate from head side oil chamber to oil tank, and both first and second boom spool valves are configured not to supply pressure oil from first and second hydraulic pumps to the boom cylinder.

This disclosure relates to a hydraulic system for a hydro-mechanical machine comprising a rotary mechanism and a boom cylinder The hydraulic system includes a primary accumulator configured to receive and store high-pressure fluid in response to starting and stopping of the rotary mechanism. A control system configured to enable passage of the high-pressure fluid stored in the primary accumulator to a rotary control valve configured to control the rotary mechanism, and a boom control valve configured to control the boom cylinder through the hydraulic supply circuit, based on a predefined pressure threshold associated with the primary accumulator. A secondary accumulator coupled to the primary accumulator and the control system via the hydraulic supply circuit is configured to store surplus high-pressure fluid provided by the primary accumulator through the hydraulic supply circuit.

A construction machine according to an exemplary embodiment of the present invention includes: an engine; a boom cylinder which is divided into a head side and a rod side; a regeneration line through which hydraulic fluid discharged from the head side of the boom cylinder moves when the boom descends; a regeneration motor which is connected with the regeneration line and is operated, and assists the engine; a pilot pump which generates a pilot pressure; a pilot line through which pilot hydraulic fluid discharged from the pilot pump moves; a regeneration connection line which connects the pilot line and the regeneration line; an on/off valve installed in the regeneration connection line; and a control device which closes the on/off valve when a pressure of the pilot line drops below a predetermined pressure or the hydraulic fluid discharged from the boom cylinder is supplied to the regeneration motor.

A control valve of hydraulic system for a working machine is provided, which includes a main body and a spool. The main body includes first, second, third, fourth and fifth ports, and first second, third, fourth and fifth inner fluid paths connected to the first, second, third, fourth and fifth ports, respectively. The spool is configured to move between a neutral position and a communicating position allowing fluid communication between the second inner fluid path and the fifth inner fluid path or between the first inner fluid path and the fifth inner fluid path. The spool includes a communicating hole configured to allow the fluid communication between the second port and the fourth port, or between the first port and the fourth port, when the spool is in a position between the communicating position and the neutral position.

A hydraulic system includes a first hydraulic actuator, a second hydraulic actuator, a first pump to supply operation fluid to the first hydraulic actuator, a second pump to supply operation fluid to the second hydraulic actuator, a second control valve to control operation fluid to be supplied from the second pump to the second hydraulic actuator, and a first control valve including a main control valve to control operation fluid to be supplied from the first pump to the first hydraulic actuator, and a subordinate control valve configured to control operation fluid to be supplied from the second pump to the second control valve and to the first hydraulic actuator. The operation fluid supplied from the second pump is confluent with operation fluid to be supplied from the first pump to the first pump, in a case of activating both of the first hydraulic actuator and the second hydraulic actuator.