Abstract: In a hydraulic drive system performing the load sensing control by using a pump device having two delivery ports whose delivery flow rates are controlled by a single pump controller, surplus flow is prevented and energy loss at an unload valve and a pressure compensating valve is reduced in combined operations in which two actuators are driven at the same time while producing a relatively large supply flow rate difference therebetween. A boom cylinder 3a is connected so that the hydraulic fluids delivered from delivery ports P1 and P2 of a pump device 1a are merged and supplied to the boom cylinder 3a. An arm cylinder 3h is connected so that the hydraulic fluids delivered from delivery ports P3 and P4 of a pump device 1b are merged and supplied to the arm cylinder 3h.

Abstract: 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.

Abstract: 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.

Abstract: 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 variable displacement type which is driven by a motor/generator, a regulator which performs variable control on the displacement volume of the hydraulic pump, a bidirectional converter which performs variable control on the revolution speed of the motor/generator, and an LS control device which controls the regulator and 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.

Abstract: 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.

Abstract: A hydraulic drive system for a track device of crawler type has right and left hydraulic track motors. The hydraulic drive system is capable of correcting for skew occurring in the straight line traveling of the track device. A traveling test is conducted upon shipment from a factory. If skew is noted during the test, a plug disposed on the side of a valve opening-side pressure receiving portion of a pressure compensating valve for the track which is lower in speed is removed and, replaced with an adjusting mechanism-mounted plug having an adjusting pin. The pin is operated so as to strengthen a biasing force of a target compensating differential pressure adjusting spring. An opening in the pressure compensating valve is thereby corrected in an opening direction and a flow rate to one of the left and right track motors is thereby adjusted to be equal to the other motor.

Abstract: 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.

Abstract: When the actuator drive torque of a hydraulic pump is lower than a switching torque ?0, a controller closes a solenoid switching valve and makes a rotary electric machine function as a generator. With the increase in the actuator drive torque, the controller controls a pressure compensated flow control valve so that the flow rate of hydraulic fluid supplied from the hydraulic pump to a rotary hydraulic device decreases. When the actuator drive torque is higher than the switching torque, the controller opens the solenoid switching valve, makes the rotary electric machine function as an electric motor, and controls the pressure compensated flow control valve so that the hydraulic fluid discharged by the hydraulic pump is not supplied to the rotary hydraulic device. Consequently, shocks due to flow rate fluctuation are prevented when operational states of the rotary hydraulic device and the rotary electric machine are switched.

Abstract: A hose looping supporter (21) is provided on an upper surface (13A) of a lid (13) of a tank body (12) constituting an operating oil tank (11). This hose looping supporter (21) is constituted by a mounting member (22) mounted on the lid (13) and four retaining arms (23) each bent in a substantially J-shape. A suction hose (19) has its midway portion adapted to be looped annularly, and this looped hose portion (19B) is mounted by being held looped by each revolving frame (23). Meanwhile, in the case of replenishing a fuel tank (15) with fuel, the suction hose (19) can be easily removed from each retaining arm (23) of the hose looping supporter (21) by reducing the diameter of the looped hose portion (19B) of the suction hose (19).

Abstract: 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.

Abstract: A hydraulic drive system for a construction machine allows automatic changes of the operational characteristics of a boom directional control valve by judging whether or not a hydraulic boom cylinder needs driving pressure at the time of a boom lowering operation. A solenoid switch valve is controlled such that a pilot oil passage with a pressure reducing valve is selected to set the limit of a boom-lowering spool stroke of a boom directional control valve to a middle position L1 when the rod-side pressure of a hydraulic boom cylinder detected by a pressure sensor is less than a threshold value and such that a pilot oil passage is selected to set the limit of the boom-lowering spool stroke of the boom directional control valve to a maximum stroke position L2 when the rod-side pressure is equal to or greater than the threshold value.

Abstract: 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.

Abstract: A hose looping supporter (21) is provided on an upper surface (13A) of a lid (13) of a tank body (12) constituting an operating oil tank (11). This hose looping supporter (21) is constituted by a mounting member (22) mounted on the lid (13) and four retaining arms (23) each bent in a substantially J-shape. A suction hose (19) has its midway portion adapted to be looped annularly, and this looped hose portion (19B) is mounted by being held looped by each revolving frame (23) . Meanwhile, in the case of replenishing a fuel tank (15) with fuel, the suction hose (19) can be easily removed from each retaining arm (23) of the hose looping supporter (21) by reducing the diameter of the looped hose portion (19B) of the suction hose (19).

Abstract: A swivel joint for a construction machine is mounted to an upper track frame, and a body is rotatable together with a swing structure main frame in an opening through engagement between a stopper projection and a stopper plate. Tubes on the swing structure side are connected to an upper end surface of the body by using fittings in concentrated layout, and tubes on the travel structure side are connected to a lower portion of the spindle by using fittings. The body has thicker wall portions in sidewalls thereof, and a plurality of axial passages communicating with a plurality of circumferential grooves are formed inside the thicker wall portions. The plurality of axial passages are opened at the upper end surface of the body, and the tubes on the swing structure side are connected to the upper end surface of the body in concentrated layout.

Abstract: 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.

Abstract: 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.

Abstract: A swivel joint for a construction machine, is mounted to an upper track frame, and a body is rotatable together with a swing structure main frame in an opening through engagement between a stopper projection and a stopper plate. Tubes on the swing structure side are connected to an upper end surface of the body by using fittings in concentrated layout, and tubes on the travel structure side are connected to a lower portion of the spindle by using fittings. The body has thicker wall portions in sidewalls thereof, and a plurality of axial passages communicating with a plurality of circumferential grooves are formed inside the thicker wall portions. The plurality of axial passages are opened at the upper end surface of the body, and the tubes on the swing structure side are connected to the upper end surface of the body in concentrated layout.

Abstract: 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.

Abstract: A differential pressure between a delivery pressure of a fixed displacement hydraulic pump 2 and a maximum load pressure among a plurality of actuators 3a to 3c is maintained at a target differential pressure by an unloading valve 5. A setting pressure of the unloading valve 5 is changed depending on an engine revolution speed by introducing a differential pressure &Dgr;Pp across a throttle 50, which is disposed in a delivery line of a fixed pump 30, to a pressure bearing sector 5d of the unloading valve. With such an arrangement, in a hydraulic drive system including an LS system, it is possible to ensure fine operability based on setting of the engine revolution speed, to perform flow rate control at a good response, and to realize superior operability.

Abstract: Differential pressures across flow control valves 6a, 6b and 6c are controlled by pressure compensating valves 7a, 7b and 7c to be held at the same value, i.e., a differential pressure &Dgr;PLS, and the differential pressure &Dgr;PLS is maintained at a target differential pressure &Dgr;PLSref by a pump displacement control unit 5. For changing the target differential pressure depending on change in revolution speed of an engine 1, a flow detecting valve 31 is disposed in a delivery line 30a, 30b of a fixed displacement hydraulic pump 30, and a differential pressure &Dgr;Pp across a variable throttle portion 31a of the flow detecting valve 31 is introduced to a setting controller 32. A selector valve 50 operable to shift between a fully closed position and a throttle position is disposed in parallel to the flow detecting valve 31 and is shifted by a control lever 51.