摘要:
In the arm-crowding or track operation, a calculating portion (700d2 or 700d4) calculates a modification gain (KAC or KTR) depending on an operation pilot pressure and a calculating portion (700g) calculates a decrease modification (DND) based on the KAC or KTR, while a calculating portion (700m or 700p) calculates a modification gain (KACH or KTRH) depending on an operation pilot pressure and calculating portions (700q-700s) calculate an increase modification (DNH) based on the KACH or KTRH. A reference target engine revolution speed NR0 is modified using the DND and DNH. In other operations than the arm-crowding and track operations, NR0 is modified using only the decrease modification (DND) calculated from the modification gain just depending on the operation pilot pressure. In the operation where an engine revolution speed is desired to become higher as an actuator load increases, the engine revolution speed can be controlled in accordance with change of the actuator load as well. In other operations, the engine revolution speed can be controlled just depending on the direction and input amount in and by which corresponding operation instructing apparatus is operated.
摘要:
A hydraulic drive system is provided with a signal guide system for guiding a delivery pressure of a pump as a command pressure via a line and a port, another signal guide system for guiding a pilot pressure of a pilot pump as another command pressure via a line and a port, a tilting control unit for controlling the displacement of the pump by the command pressures guided to the ports, a controller having a command current-setting unit for setting a relationship between a target engine speed and a command current, a target engine speed-indicating unit for an engine, and a solenoid-operated proportional valve for allowing the pilot pressure of the line to pass as is while no drive signal is outputted from the controller but for being reduced in opening to change the pilot pressure to a smaller value when a drive signal is outputted from the controller.
摘要:
A hydraulic control system according to the present invention for a construction machine is provided with a directional control valve switchable by a pilot control valve, a hydraulic cylinder, a pilot pump, a selector valve for selecting one of a maximum value out of pilot pressures of the pilot control valve, a flow control unit for controlling the flow rate of a variable displacement hydraulic pump, a pressure-reducing valve for converting a delivery pressure of the pilot pump to a pump control signal, which controls driving of the flow control unit, in accordance with a pilot pressure guided to a first signal line connected to the selector valve, a branch line connecting the pilot pump and the pressure-reducing valve with each other, and a second signal line for guiding the pump control signal, which has been converted at the pressure-reducing valve, to the flow control unit.
摘要:
A reference pump-delivery-rate calculating portion calculates a reference delivery rate of a hydraulic pump by referring to a table stored in a memory based on a control pilot pressure for the hydraulic pump. A target pump-delivery-rate calculating portion divides the reference delivery rate by a ratio of a maximum revolution speed to a target engine revolution speed, thereby calculating a target delivery rate. A target pump tilting calculating portion divides the target delivery rate by an actual engine revolution speed and a constant, thereby calculating a target tilting. A solenoid output current calculating portion calculates a drive current to provide the target tilting and outputs the drive current to a solenoid control valve. The pump delivery rate is thereby controlled with good response following input change of an operation instructing device.
摘要:
Provided are hydraulic pumps 1,2, a control valve group 15a connected to the pump 1 and including a bypass on/off valve 7, a control valve group 15b connected to the pump 2 and including a reserve-actuator-controlling, directional control valve 11, a communication line 13 communicating a most upstream side of the control valve group 15a with a supply line 11a to the reserve-actuator-controlling, directional control valve 11, a merge control valve 14 for communicating or cutting off the communication line 13, an interlocked control means for changing over the merge control valve 14 to an open position and the bypass on/off valve 7 to a closed position in association with a change-over operation of the reserve-actuator-controlling, directional control valve 11, and a selective control valve 28 capable of taking one of a state, in which the operation to change over the merge control valve 14 by the interlocked control means is feasible, and another state in which the operation to change over the merge control valve by the interlocked control means is infeasible. The control valve group 15a, the control valve group 15b, the communication line 13 and the merge control valve 14 are arranged in a housing 15 such that a change or the like in a maximum value of an operating speed of an actuator, said operating speed being controlled by the reserve directional control valve, can be achieved.
摘要:
A hydraulic circuit system includes a shuttle block, and shuttle valves are arranged and connected within the shuttle block. The maximum pressure in a predetermined operation signal pressure group selected from operation signal pressures generated by pilot operating units is selected to produce a control signal pressure within the shuttle block. The control signal pressure is output to control devices such as a track communicating valve, a swing brake cylinder, and regulators for hydraulic pumps.
摘要:
A controller 520 has a data portion 520c in which the relationship between a pump delivery pressure and a target opening area of a variable throttle 300a of a control valve 300 is set such that the target opening area is large when the pump delivery pressure is low, and small when the pump delivery pressure is high. An input portion 520a takes in a detection signal from a pump pressure sensor 700, a processing portion 520b reads the data from the data portion 520c and calculates a signal output to a solenoid proportional valve 590, and an output portion 520d converts the calculated signal into a command signal for the solenoid proportional valve 590 and outputs the command signal. Upon receiving the command signal from the controller 520, the solenoid proportional valve 590 produces a command pilot pressure for the control valve 300 corresponding to the input signal and controls the opening area of the variable throttle 300a.
摘要:
A hydraulic system for a construction machine includes a hydraulic pump driven by a prime mover, actuators driven by a hydraulic fluid delivered from the hydraulic pump, flow control valves for controlling flow of the hydraulic fluid to the actuators and operation means for operating the flow control valves. A relief value sets a relief pressure for limiting the maximum delivery pressure of the hydraulic pump and relief pressure change means increase or decrease the relief pressure set by the relief valve. The relief pressure change means automatically increase or decrease the relief pressure in accordance with the input amount of the operation means.
摘要:
For enabling a boom to be smoothly raised during the triple combined operation of boom-up, arm-crowd and bucket-crowd in a hydraulic circuit system for a hydraulic excavator, in a first valve group of a hydraulic valve apparatus (12), a variable throttle valve (70) is installed in a feeder passage (32) of a bucket directional control valve (21) downstream of a load check valve (32a), and a secondary pressure C as a boom-up operation command is introduced through a line (71) to a pilot control sector (70a) of the variable throttle valve (70) which sector operates in the throttling direction, so that when the secondary pressure C is 0 or small, the variable throttle valve (70) is fully opened and, as the secondary pressure C increases, an opening area of the variable throttle valve (70) is reduced to restrict the flow rate of a hydraulic fluid supplied through the bucket directional control valve (21).
摘要:
A joining directional control valve 13 is disposed to supply, to an arm cylinder 4, not only a hydraulic fluid delivered from a first hydraulic pump 1, but also a hydraulic fluid delivered from a second hydraulic pump 2 when an arm directional control valve 14 is driven. Respective delivery pressures of the hydraulic pumps 1, 2 are detected by pressure sensors 101, 102, and the opening area of a recovery control valve 6 is controlled depending on a lower one of the detected pressures from the pressure sensors 101, 102 such that, even in the combined operation of the arm cylinder 4 and another actuator 3, 4, the hydraulic fluid can be recovered for return to the arm cylinder 4 when the load pressure of the arm cylinder 4 is low. Thus, by supplying the hydraulic fluids from the two hydraulic pumps to the particular actuator for which the hydraulic fluid is to be recovered, a recovery flow rate is ensured when the load of the particular actuator is low in the combined operation.