Provided is a work vehicle which can prevent an engine from stalling regardless of type of a system mounted on a vehicle body. In a wheel loader 1 equipped with a loading work device 11 operated by an electric operation lever 19, first and second directional control valves 5, 6 include neutral positions 5N, 6N for causing hydraulic oil discharged from a hydraulic pump 12 to return to a hydraulic oil tank 10, respectively, and in the case where a discharge pressure P of the hydraulic pump 12 is a main relief pressure Pr or more and an engine rotational speed N is less than a low idle rotational speed NL, a controller 2, 2A restricts the output of control signals to first and second solenoid control valves 3, 4 so as to cause the first and second directional control valves 5, 6 to be switched to the neutral positions 5N, 6N, respectively.

A system for controlling hydraulic fluid flow within a work vehicle includes a load sense valve configured to adjust the pressure of a bleed flow within a load sense conduit. Moreover, the system includes a computing system configured to determine the pressure of the hydraulic fluid within the fluid supply conduit downstream of the flow control valve based on the data captured by a pressure sensor. Furthermore, the computing device is configured to control an operation of the load sense valve to selectively adjust the pressure of the bleed flow within the load sense conduit based on the determined pressure.

A pilot hydraulic system may include a pilot pressure source, a pilot pressure return tank, a pilot valve, a pilot pressure supply line connecting the pilot pressure source to the pilot valve, and a pilot pressure return line connecting the pilot pressure return tank to the pilot valve. A main control valve may include a pilot chamber. A pilot pressure control line connects the pilot valve to the pilot chamber. A hydraulic sub-system is provided for modifying pilot pressure provided to the pilot chamber of the main control valve. The hydraulic sub-system may include a variable orifice valve disposed in the pilot pressure control line, a pilot pressure bypass line communicating the pilot pressure control line downstream of the variable orifice valve with the pilot pressure return line, and an electrohydraulic pressure reducing valve (EHPRV) disposed in the pilot pressure bypass line.

The present invention pertains to an air cylinder (10) in which flow rate controllers (24, 24A) are built into a head cover (14) and a rod cover (16), said flow rate controllers (24, 24A) being provided with a first flow rate adjustment part (28) connected between a port (14a, 16a) and a cylinder chamber (12c), a second flow rate adjustment part (32) provided adjacent to the first flow rate adjustment part (28), and a pilot check valve (38) connected in series to the second flow rate adjustment part (32). In response to the pressure of pilot air, the pilot check valve (38) switches between a state in which the passage of exhaust air from the cylinder chamber (12c) is permitted and a state in which the passage of exhaust air is prevented.

A shovel includes a lower traveling body, an upper traveling body turnably mounted on the lower traveling body, a hydraulic actuator, an operating apparatus configured to be operated to operate the hydraulic actuator, an object detector configured to detect an object within a predetermined area around the shovel, a gate lock lever configured to switch the operating apparatus between an enabled state and a disabled state, and a control device. The control device is configured to switch the operating apparatus between the enabled state and the disabled state separately from the gate lock lever, and to disable the operating apparatus in response to determining that the object is present within the predetermined area based on the output of the object detector while the operating apparatus is switched to the enabled state by the gate lock lever, during the standby state of the shovel.

A hydraulic system for a working machine includes a hydraulic pump to output a hydraulic fluid, an operation device operable to supply a pilot fluid in accordance with an amount by which the operation device is operated, a hydraulic actuator to be operated by the hydraulic fluid, a pilot fluid passage connected to the operation device, a first control valve connected to the pilot fluid passage and to be operated by the pilot fluid to control a flow of the hydraulic fluid, a second control valve to be operated by the pilot fluid to control a flow of the hydraulic fluid, a proportional valve to change a pressure of the pilot fluid to operate the second control valve, a pressure detector provided in the pilot fluid passage to detect a pressure in the pilot fluid passage, and a controller to control the proportional valve based on the pressure.

A flow rate controller and a drive device are provided with a cylinder flow passage connected to an air cylinder; a main flow passage for supplying air to and discharging air from the air cylinder; an auxiliary flow passage that has a first throttle valve and through which exhaust air discharged from the air cylinder passes with a smaller flow rate than that of the main flow passage; a switch valve that switches between a first position in which the cylinder flow passage communicates with the main flow passage and a second position in which the cylinder flow passage communicates with the auxiliary flow passage; and a pilot air adjustment part that guides a portion of the exhaust air from the air cylinder as pilot air to the switch valve.

In accordance with one embodiment of the present disclosure, a material moving machine comprises a pilot hydraulic switching system. The pilot hydraulic switching system comprises a control unit, a first directional valve, and a second directional valve. The control unit is configured to operate the first and second directional valves to shift a variable position actuator valve between a static state, a retract state, and an extend state. The actuator valve comprises a first and second control element. In the retract and extend states, the first and second directional valves control fluid flow to the variable position actuator valve with a positive net pressure on either the first or second control elements and a negative net pressure on the other control element to move the material moving implement. In the static state, the first and second directional valves control fluid flow equally on the first and second control elements.

An air cylinder in which a flow rate controller is built in, has a head cover and a rod cover. A pilot air adjustment unit guides exhaust air to a switch valve of the flow rate controller as pilot air, and the switch valve is switched by an increase in the pressure of the pilot air.

A flow rate controller and a drive device are provided with a first flow passage connected between an operation switching valve and an air cylinder, and that supplies air to and discharges air from a cylinder chamber of the air cylinder; a first flow rate adjustment part provided in the first flow passage; a second flow passage adjacent to the first flow passage; a pilot check valve provided at a point along the second flow passage; a second flow rate adjustment part connected in series to the pilot check valve at a point along the second flow passage; a pilot air flow passage, one end of which communicates with the operation switching valve and the other end of which is connected to a pilot port of the pilot check valve; and a third flow rate adjustment part provided in the pilot air flow passage.