A hydraulic system of a work machine includes a first hydraulic actuator, a first control valve, a first oil passage, a second hydraulic actuator, a second control valve, a second oil passage, and a bypass oil passage. The first control valve is connected to the first hydraulic actuator to control the first hydraulic actuator. The first oil passage is connected to the first control valve to supply hydraulic oil to the first control valve. The second control valve connected to the second hydraulic actuator to control the second hydraulic actuator. The second oil passage connects the second control valve and the first hydraulic actuator via the first control valve. Hydraulic oil returning from the first hydraulic actuator to the first control valve is to be supplied to the second control valve through the second oil passage. The bypass oil passage connects the first oil passage and the second oil passage.

A method of assembling a solenoid valve assembly is disclosed. The method includes inserting an axial end of a valve housing partially through an aperture of a tab. The axial end of the valve housing extends partially through an opening of a solenoid housing. An interlocking element is positioned in a first axial end of the solenoid housing. The method includes inserting a petal of the valve housing into a pocket of the interlocking element. The method includes engaging the interlocking element with an installation tool and rotating the installation tool to rotate the interlocking element and the valve housing until a lip of the solenoid housing is axially positioned between (1) the petal of the valve housing and (2) a protrusion of the tab, such that the valve housing, the tab, and the solenoid housing are fixed to each other.

A hydraulic system includes a first hydraulic device, a second hydraulic device, a first control valve to control the first hydraulic device, a second control valve disposed on a downstream side of the first control valve and configured to control the second hydraulic device, a communication tube connecting the first hydraulic device to the first control valve, a supply fluid tube connecting the first control valve to the second control valve, a connection fluid tube disposed on the first control valve, the connection fluid tube connecting the communication tube to the supply fluid tube, a discharge fluid tube connected to the first control valve, a setting portion disposed on the discharge fluid tube and configured to increase a pressure in the discharge fluid tube, a branching fluid tube branched from the connection fluid tube and connected to the discharge fluid tube, and a throttle disposed on the branching fluid tube.

An inner oil passage (45) is formed inside a slidable spool (22). The slidable spool (22) defines, in its circumferential face, a first opening (46), a second opening (47) and a third opening (48). The first opening (46), the second opening (47) and the third opening (48) are communicated to the inner oil passage (45). When the slidable spool (22) is switched to a floating position (F), the first the first opening (46) is aligned with a first port end portion (25a), the second opening (47) is aligned with a second port end portion (26a), and the third opening (48) is aligned with a fourth port end portion (24a), respectively, and a first cylinder port and a second cylinder port are communicated to a tank port (24) via the inner oil passage (45).

A method of assembling a solenoid valve assembly is disclosed. The method includes inserting an axial end of a valve housing partially through an aperture of a tab. The axial end of the valve housing extends partially through an opening of a solenoid housing. An interlocking element is positioned in a first axial end of the solenoid housing. The method includes inserting a petal of the valve housing into a pocket of the interlocking element. The method includes engaging the interlocking element with an installation tool and rotating the installation tool to rotate the interlocking element and the valve housing until a lip of the solenoid housing is axially positioned between (1) the petal of the valve housing and (2) a protrusion of the tab, such that the valve housing, the tab, and the solenoid housing are fixed to each other.

Exemplary control valves that may be configured as a load sense, closed-center, and/or open-center valve. The control valve may include optional individual valve force sensing to potentially allow an operator to smoothly operate devices operating on low-load work ports even when a variable displacement pump is inducing pressure to operate a device connected to a high-load work port of a separate valve or worksection in the same stack. This optional force sensing may be employed on any or all worksections associated with any valve stack, and may further be included on one or both workports for any given worksection. Each worksection may include parallel and variable paths of fluid supplied by the pump. Also, flow priority to one or more worksections or external valves in a corresponding hydraulic system is optional and can be customized using the variable flow path and a corresponding fixed restriction.

A hydraulic drive system of construction machine includes: first and second pumps that are driven by an engine; boom control valve disposed on circulation line extending from first pump and connected to boom cylinder by boom raising supply line and boom lowering supply line; first suction line that leads hydraulic oil from a tank to first pump; second suction line that leads hydraulic oil from tank to second pump; regenerative line, through which hydraulic oil discharged from boom cylinder flows, regenerative line extending from boom control valve or boom raising supply line and being connected to at least one of the first and second suction lines; check valve provided on first suction line and/or second suction line, check valve being positioned upstream of where regenerative line is connected to first suction line and/or second suction line; and relief valve provided on relief line that communicates with regenerative line.

An inner oil passage (45) is formed inside a slidable spool (22). The slidable spool (22) defines, in its circumferential face, a first opening (46), a second opening (47) and a third opening (48). The first opening (46), the second opening (47) and the third opening (48) are communicated to the inner oil passage (45). When the slidable spool (22) is switched to a floating position (F), the first the first opening (46) is aligned with a first port end portion (25a), the second opening (47) is aligned with a second port end portion (26a), and the third opening (48) is aligned with a fourth port end portion (24a), respectively, and a first cylinder port and a second cylinder port are communicated to a tank port (24) via the inner oil passage (45).

A shuttle valve includes: a first valve body; a second valve body, a first control-pressure-charged surface and a second control-pressure-charged surface of the first valve body being larger than a third control-pressure-charged surface and a fourth control-pressure-charged surface of the second valve body, a first control pressure from a first inlet pressure port being applied to a first valve body first side, the first control pressure from a second inlet pressure port being applied to a first valve body second side, a second control pressure from a third inlet pressure port being applied to a second valve body first side, the second control pressure from a fourth inlet pressure port being applied to a second valve body second side, a first control pressure acting on a first control-pressure-charged surface and a second control-pressure-charged surface, and the second control pressure acting on a third control-pressure-charged surface and a fourth control-pressure-charged surface.

A hydraulic cylinder causes a work implement to be lowered due to the exhaust of hydraulic fluid from a first chamber and the supply of hydraulic fluid to a second chamber. A hydraulic fluid flowpath has a first flowpath and a second flowpath. The first flowpath connects a first pump port and the first chamber. The second flowpath connects a second pump port and the second chamber. The hydraulic fluid flowpath configures a closed circuit between a hydraulic pump and the hydraulic cylinder. A bleed-off flowpath branches off from the first flowpath. A portion of hydraulic fluid exhausted from the first chamber when lowering the work implement flows into the bleed-off flowpath.