摘要:
An electric drive unit for a construction machine is capable of increasing the operating time of the construction machine. The electric drive unit has an electricity storage device, a hydraulic pump of the fixed displacement type which is driven by a motor/generator, a plurality of directional control valves which respectively control the flow of hydraulic fluid supplied to a plurality of hydraulic actuators, a bidirectional converter which performs variable control on the revolution speed of the motor/generator, and an LS control device which controls the bidirectional converter so that LS differential pressure Pls equals a target value Pgr. The bidirectional converter performs regeneration control for converting the inertial force of the rotor of the motor/generator into electric power thereby charging the electricity storage device when the revolution speed of the motor/generator is decreased in response to an excess of the LS differential pressure Pls over the target value Pgr.
摘要:
A hydraulic drive system executing load sensing control is capable of efficiently combusting and removing filter deposits inside an exhaust gas purification device by pump output power increasing control when there is no actuator operation, eliminating interference between the actuator operation and the pump output power increasing control. A first solenoid selector valve selects between tank pressure and delivery pressure of a pilot pump. A second solenoid selector valve is arranged in a line leading the output pressure of a differential pressure reducing valve to an LS control valve for selecting between enabling and disabling of the load sensing control. When the exhaust gas purification device needs regeneration, a controller executes switching to make the first solenoid selector valve output the delivery pressure of the pilot pump as dummy load pressure and to make the second solenoid selector valve disable the load sensing control.
摘要:
A main relief valve 13 includes a biasing force altering unit 60, which constitutes, in combination with a gate lock valve 23 and a gate lock lever 24, relief pressure altering means for manually switching the relief pressure of the main relief valve 13 between a first pressure (a standard pressure of 25 MPa, for example) and a second lower pressure for engine start-up (e.g., 3.0 MPa). This allows the main relief valve 13 to return the hydraulic fluid discharged from a hydraulic pump 2 to a tank T in conjunction with an unloading valve 9 when multiple actuators 5a, 5b, . . . are not in operation under the ambient temperature below freezing point. As a result, it is possible to reduce the load on the hydraulic pump during cold engine start-up without compromising the anti-hunting characteristics of the unloading valve, thereby improving the engine start-up performance.
摘要:
An electric drive unit for a construction machine is capable of increasing the operating time of the construction machine. The electric drive unit has an electricity storage device, a hydraulic pump of the fixed displacement type which is driven by a motor/generator, a plurality of directional control valves which respectively control the flow of hydraulic fluid supplied to a plurality of hydraulic actuators, a bidirectional converter which performs variable control on the revolution speed of the motor/generator, and an LS control device which controls the bidirectional converter so that LS differential pressure Pls equals a target value Pgr. The bidirectional converter performs regeneration control for converting the inertial force of the rotor of the motor/generator into electric power thereby charging the electricity storage device when the revolution speed of the motor/generator is decreased in response to an excess of the LS differential pressure Pls over the target value Pgr.
摘要:
A main relief valve 13 includes a biasing force altering unit 60, which constitutes, in combination with a gate lock valve 23 and a gate lock lever 24, relief pressure altering means for manually switching the relief pressure of the main relief valve 13 between a first pressure (a standard pressure of 25 MPa, for example) and a second lower pressure for engine start-up (e.g., 3.0 MPa). This allows the main relief valve 13 to return the hydraulic fluid discharged from a hydraulic pump 2 to a tank T in conjunction with an unloading valve 9 when multiple actuators 5a, 5b, . . . are not in operation under the ambient temperature below freezing point. As a result, it is possible to reduce the load on the hydraulic pump during cold engine start-up without compromising the anti-hunting characteristics of the unloading valve, thereby improving the engine start-up performance.
摘要:
A hydraulic drive system for a construction machine has a travel detection device which detects whether or not the operation mode is a traveling operation and a setting changing device. The setting changing device sets the target differential pressure of load sensing control at an absolute pressure Pa when the operation mode is not a traveling operation, and sets the target differential pressure of the load sensing control at an absolute pressure Pa′ rather than the absolute pressure Pa. In this way, in the actuator operation other than traveling, a necessary actuator speed can be obtained and supplied with the necessary maximum flow rate. In addition, during the combined operation, a flow rate in accordance with the opening area ratios of flow control valves can be distributed to actuators different in load pressure from one another; and energy efficiency is enhanced due to less energy loss during traveling operation.
摘要:
A hydraulic drive system executing load sensing control is capable of efficiently combusting and removing filter deposits inside an exhaust gas purification device by pump output power increasing control when there is no actuator operation, eliminating interference between the actuator operation and the pump output power increasing control. A first solenoid selector valve selects between tank pressure and delivery pressure of a pilot pump. A second solenoid selector valve is arranged in a line leading the output pressure of a differential pressure reducing valve to an LS control valve for selecting between enabling and disabling of the load sensing control. When the exhaust gas purification device needs regeneration, a controller executes switching to make the first solenoid selector valve output the delivery pressure of the pilot pump as dummy load pressure and to make the second solenoid selector valve disable the load sensing control.
摘要:
To permit driving a tilt cylinder and an angle cylinder at relatively low speed and also to permit driving an additional actuator at high speed.Provided are a tilt cylinder 9 and angle cylinder 10 for pivotally tilting a blade 7 selectively leftward and rightward and for pivotally angling the blade 7 selectively forward and rearward, respectively, and an additional actuator for actuating an additional attachment. Also provided are a tilting/angling pressure oil feed means comprising a tilting/angling directional control valve 19 for controlling a flow of pressure oil to be fed to one of the cylinders 9,10 and a selector valve 20 for selectively feeding pressure oil, which flows out of the directional control valve 19, to one of the cylinders 9,10. An additional pressure oil feed means for feeding pressure oil to the additional actuator 27 is provided independently of the tilting/angling directional control valve, and the additional pressure oil feed means has an additional directional control valve 29.
摘要:
The hydraulic drive system comprises an engine 1, a pump unit 100, a plurality of actuators 5a, 5b and 5c, a control valve unit 4, and engine revolution speed detecting means 4f. The pump unit 100 includes a pump tilting control mechanism 8 for load sensing control, and the control valve unit 4 includes a plurality of flow control valves 15a, 15b and 15c and pressure compensation valves 10a, 10b and 10c. The engine revolution speed detecting means 4f includes a first differential pressure reducing valve 14 for outputting, as an absolute value, a pressure depending on an engine revolution speed. The output pressure of the first differential pressure reducing valve 14 is introduced, as a target load-sensing differential pressure, to the pump tilting mechanism 8 via a line 127.
摘要:
A winding and cutting machine for rolled paper provided with a roller shaft holding a roll from an inner side, a feeding roller and a feeding aid roller to hold and pull the paper for a predetermined length, and a fixed cutting blade disposed between the feeding roller and a winding rotational body which is constructed as to press the paper to the fixed cutting blade into the predetermined length by winding the paper and giving tensile force to the paper.