A priority function control apparatus for a construction machine and a control method thereof are disclosed, which enable an operator to set the order of preference or the extent of preference of an optional device in the case where a work is done through replacement of the optional device attached to an excavator. The priority function control apparatus includes a hydraulic pump and a pilot pump; an optional device and an attachment connected to the hydraulic pump; an attachment operation lever outputting an operation signal when an operator performs an operation; an optional device spool controlling a flow direction of hydraulic fluid that is supplied from the hydraulic pump to the optional device; an attachment spool controlling an amount and a flow direction of the hydraulic fluid supplied from the hydraulic pump to the attachment; an electrical operation device for the optional device; an electro proportional reducing valve outputting secondary signal pressure that corresponds to the operation signal of the electrical operation device for the optional device; a first pressure detection sensor detecting in real time signal pressure depending on the operation amount of the attachment operation lever to output a detection signal; and a controller limiting the signal pressure that is applied from the electro proportional reducing valve to the optional device spool by the operation of the electrical operation device for the optional device to a preset signal pressure if a priority function is applied depending on the operation amount of the attachment through detection of the first pressure detection sensor.

A construction machine, comprising a hydraulic pump, a swing hydraulic motor, a swing electric motor, a delivery capacity regulating device, and a control unit which controls the driving/braking of the swing structure, is configured to comprise an operation amount detection device for detecting the operation amount of the swing control lever and a speed detection device for detecting the speed of the swing electric motor. The control unit includes a hydraulic pump output reduction control unit which takes in an operation amount signal representing the operation amount of the swing control lever detected by the operation amount detection device and a speed signal representing the speed of the swing electric motor detected by the speed detection device and controls the delivery capacity regulating device by calculating a reduction rate of the output of the hydraulic pump based on the detection signals.

A working machine includes a first traveling fluid passage connected to a first pressure-receiving portion, a second traveling fluid passage connected to a second pressure-receiving portion, a third traveling fluid passage connected to a third pressure-receiving portion, a fourth traveling fluid passage fluidly connected to a fourth pressure-receiving portion, and a connection fluid passage connecting at least two of the first, second, third and fourth pressure-receiving portions to each other. When a traveling operation member is operated, operation fluid flows to the first pressure receiving portion through the first traveling fluid passage, to the second pressure receiving portion through the second traveling fluid passage, to the third pressure receiving portion through the third traveling fluid passage, and to the fourth pressure receiving portion through the fourth traveling fluid passage.

A working machine includes a prime mover, a hydraulic pump driven by power of the prime mover, a cooler including a cooling fan rotated by either the power of the prime mover or hydraulic fluid delivered from the hydraulic pump, and a controller configured or programmed to perform a reduction control for reducing a target fan rotation speed that is a target rotation speed of the cooling fan in response to reduction of an actual prime mover rotation speed that is an actual rotation speed of the prime mover, and to perform, after the reduction control, a restoration control for restoring the target fan rotation speed. The controller is configured or programmed to make a difference between a reduction rate of the target fan rotation speed in the reduction control and an increase rate of the target fan rotation speed in the restoration control.

Disclosed is a hydraulic circuit for construction equipment for controlling to selectively supply a hydraulic oil from a hydraulic pump to a hydraulic cylinder for driving a boom. The hydraulic circuit for construction equipment, according to the present invention, comprises: a hydraulic cylinder driven by a hydraulic oil of a hydraulic pump; a direction control valve installed on the oil passage between the hydraulic pump and the hydraulic cylinder; an operating device installed on the oil passage between a pilot pump and the direction control valve; a center by-pass switching valve installed at the most downstream side of a center by-pass passage of the hydraulic pump; a pressure detection sensor that detects the pressure of a hydraulic oil at the large chamber side of the hydraulic cylinder; a jack-up switching valve installed on the oil passage between the operating device and the center by-pass switching valve; and a flow control valve installed in the spool of the direction control valve.

Disclosed is an apparatus for improving excavating operation characteristic and grading operation characteristic of an excavator. The apparatus includes a solenoid valve group and a hydraulically controlled selector valve. An oil controlling output A1 of the solenoid valve group is configured in series with oil controlling input a1 of the hydraulic control valve. An oil controlling output A2 of the solenoid valve group is configured in series with a pilot control end XBa2 of a multi-port valve group. An oil return port T1 of the solenoid valve group is connected to the hydraulic oil tank. An oil controlling output b1 of the hydraulically controlled selector valve is connected to a pilot control end XAb2 of the multiplexer valve group, and an oil return port T2 of the hydraulically controlled selector valve is connected with the hydraulic oil tank. The apparatus improves operational efficiency and control comfortability.

A working machine is disclosed. A boom supports an arm. An upper revolving body supports the boom. A lower traveling body mounts the upper revolving body in a rotatable state. A hydraulic actuator drives a hydraulic oil while relieving the hydraulic oil. A first pump supplies the hydraulic oil to the hydraulic actuator. A pump state detector detects load of the first pump. A controller reduces a flow rate of the hydraulic oil from the first pump to the hydraulic actuator when the pump state detector detects a predetermined state.

It is to provide a control valve that can make the valve body smaller and the structure simplified and the hydraulic pressure system equipped therewith. The plural number of parallel feeder oil paths that are respectively connected to the plural number of pumps and are not cut off by displacement of spools is provided in the valve body in a linearly through all spool holes. For each section, a connection oil path is provided to connect any one side of parallel feeder oil paths to the bridge circuit B of the internal spools. Parallel feeder oil paths can be positioned in a simple shape, but also, just by properly providing connection oil paths, without depending on each section belonging to any of pump systems, positioning of section can be freely done within the valve body. Making the valve body smaller and the structure simplification can be executed.

Provided is a hydraulic drive apparatus including a specific working actuator making a working arm perform a traveling assist motion upon the slip, first and second traveling motors, first and second hydraulic pumps, a traveling selector valve switchable to a neutral position and a straight traveling position, a communication throttle portion between a working fluid passage and a traveling fluid passage in the straight traveling position, and a switching control part switching the traveling selector valve to the neutral position when a single operation action is performed and to the straight traveling position when a specific combined operation action including a forward traveling operation and the specific working operation is performed. The switching control section adjusts the opening of the communication throttle section to decrease the flow rate therethrough with an increase in the difference between the first and second pump pressures.

Provided is a hydraulic drive system including: first and second pumps; a first main supply fluid line and an optional supply fluid line leading to the first pump; a second main supply fluid line leading to the second pump; a main manipulating device for the main actuator; an optional manipulating device for the optional actuator; a bleed-off flow rate regulating section to change the bleed-off flow rate for the second pump; and a bleed-off control section to operate the bleed-off flow rate regulating section to change the discharge flow rate of the second pump in accordance with a control operation applied to the main manipulating device and to make a bleed-off flow rate in a specific combined manipulation state with simultaneous performance of a specific main control operation and an optional control operation be smaller than that in a single main manipulation state.