摘要:
A priority valve 7 is disposed between a hydraulic pump 2 and a steering valve 4 and is used to supply priority steering cylinders 103a and 103b with pressurized oil discharged from the hydraulic pump 2 by controlling the differential pressure across a meter-in hydraulic line of the steering valve 4 such that the differential pressure is kept at a target value. A pressure sensor 31 for detecting the load pressures of the steering cylinders 103a and 103b is provided. On the basis of the detected load pressures, the target value set for the priority valve 7 is modified by devices including a controller 32, a solenoid valve 33, a pilot hydraulic line 29, and a pressure receiving unit 24c of the priority valve 7. The above configuration enables suppression of a shock occurring at the start of turning of the steering wheel.
摘要:
A priority valve 7 is disposed between a hydraulic pump 2 and a steering valve 4 and is used to supply priority steering cylinders 103a and 103b with pressurized oil discharged from the hydraulic pump 2 by controlling the differential pressure across a meter-in hydraulic line of the steering valve 4 such that the differential pressure is kept at a target value. A pressure sensor 31 for detecting the load pressures of the steering cylinders 103a and 103b is provided. On the basis of the detected load pressures, the target value set for the priority valve 7 is modified by devices including a controller 32, a solenoid valve 33, a pilot hydraulic line 29, and a pressure receiving unit 24c of the priority valve 7. The above configuration enables suppression of a shock occurring at the start of turning of the steering wheel.
摘要:
A hydraulic drive device for a hydraulic excavator, includes: a first hydraulic pump; a first boom directional control valve and a second arm directional control valve which are connected in parallel to the first pump; a second hydraulic pump; and a second boom directional control valve and a first arm directional control valve which are connected in parallel to the second pump; wherein: the hydraulic drive device also includes: a third hydraulic pump; a third boom directional control valve connected to the third pump and controlling the flow of pressure oil supplied to a boom cylinder; and a third arm directional control valve connected in tandem with the third boom directional control valve and controlling the flow of pressure oil supplied to an arm cylinder.
摘要:
A hydraulic drive device for a hydraulic excavator, includes: a first hydraulic pump; a first boom directional control valve and a second arm directional control valve which are connected in parallel to the first pump; a second hydraulic pump; and a second boom directional control valve and a first arm directional control valve which are connected in parallel to the second pump; wherein: the hydraulic drive device also includes: a third hydraulic pump; a third boom directional control valve connected to the third pump and controlling the flow of pressure oil supplied to a boom cylinder; and a third arm directional control valve connected in tandem with the third boom directional control valve and controlling the flow of pressure oil supplied to an arm cylinder.
摘要:
In a cooling fan drive system for a travel type working machine, the rotational speed of a cooling fan is controlled to the optimum rotational speed in accordance with temperature increase of the temperature of an engine cooling water, and the engine rotational speed is smoothly increased when the engine rotational speed is increased under travel acceleration. A fourth fan target rotational speed calculator 35e and a minimum value selector 35f are provided, and under non-operation, the fan target rotational speed is set to a low rotational speed irrespective of the temperature. When an acceleration pedal 12 is depressed to increase the rotational speed of the engine under travel acceleration, the increase of the drive pressure of a hydraulic motor 23 due to increase of the rotation of the cooling fan 9 is suppressed, and the load on the engine 1 is reduced.
摘要:
In a cooling fan drive system for a travel type working machine, the rotational speed of a cooling fan is controlled to the optimum rotational speed in accordance with temperature increase of the temperature of an engine cooling water, and the engine rotational speed is smoothly increased when the engine rotational speed is increased under travel acceleration. A fourth fan target rotational speed calculator 35e and a minimum value selector 35f are provided, and under non-operation, the fan target rotational speed is set to a low rotational speed irrespective of the temperature. When an acceleration pedal 12 is depressed to increase the rotational speed of the engine under travel acceleration, the increase of the drive pressure of a hydraulic motor 23 due to increase of the rotation of the cooling fan 9 is suppressed, and the load on the engine 1 is reduced.
摘要:
The operability when performing a combined arm-crowd and bucket operation can be improved. A hydraulic drive device for a hydraulic excavator includes: a bucket directional control valve and a second arm directional control valve, which are connected in parallel tandem with a first hydraulic pump; a first arm directional control valve that is connected to a second hydraulic pump; and a flow rate restriction device that restricts the flow rate of pressure oil supplied to the second arm directional control valve, during crowd operation of a bucket. This flow rate restriction device includes a variable throttle whose opening is controlled so as to become smaller as a bucket operating device is operated to the crowd side, the variable throttle being provided in a bypass path connecting to the supply port of the second arm directional control valve.
摘要:
To provide a steering system for a construction vehicle, which is suited not only for traveling on general roadways but also for work at construction sites and can perform high-reliability steering control.A steering system for a construction vehicle is provided with a directional control valve 5 for controlling a flow of pressure oil to body-articulating hydraulic cylinders 2 that perform steering and also with a steering-wheel-operated signal generation means 6 for outputting by operation of a steering wheel 7a a pilot signal to the directional control valve 5 for switching the valve 5. The steering system is also provided with a lever-operated signal generation means for producing by operation of a lever 10a a pilot signal to switch the directional control valve 5, said lever-operated signal generation means including pressure-proportional solenoid valves 12a,12b or the like, selector valves 13a,13b switchable to permit selectively outputting the pilot signal from one of the signal generation means to the directional control valve 5, and an automated switching means for switching the selector valves 13a,13b such that upon operation of the steering wheel 7a, the pilot signal from the steering-wheel-operated signal generation means 6 can be preferentially outputted to the directional control valve 5.
摘要:
A hydraulic steering unit 5 generates a control pressure corresponding to the rotational quantity and rotational direction of the steering wheel 109 on the basis of pressurized oil of a pilot pump 13. Signals of pressure sensors 6a and 6b used to detect the control pressure, and a signal of a front operation detection unit 31, are inputted into a controller 132. A controller 32 and solenoid valves 33a and 33b control a stroke of a steering valve 4 so that the stroke becomes larger with increase in control pressure detected by each of the pressure sensors 6a and 6b. In addition when the operation of a front work device is detected, the controller 32 and the solenoid valves 33a and 33b control the stroke of the steering valve 4 so that the stroke becomes larger than that provided when the operation of the front work device is not detected.
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.