Abstract: In a hydraulic excavator including a track structure, a swing structure swingably disposed on an upper portion of the track structure, a work implement coupled to the swing structure, an earth removal device including a blade coupled to the track structure and a lift cylinder configured to raise and lower the blade, an operation sensor configured to detect an operation of a travelling lever, a height sensor configured to measure a height of the blade with respect to the track structure, an antenna for a satellite positioning system, the antenna being mounted on the swing structure, and a controller configured to calculate positional data regarding the blade, the controller is configured to determine a travelling operation on the basis of a signal of the operation sensor, calculate a travelling direction of straight forward travelling of the track structure as an orientation of the track structure when the straight forward travelling of the track structure is detected from a trajectory of the antenna with a st

Abstract: To provide a work machine having a blade provided to a track structure, and a swing structure provided swingably on the upper side of the track structure, which work machine allows for computation of the horizontal coordinates of the blade. The work machine includes: a swing-structure-position acquiring device that acquires a horizontal coordinate and an orientation of the swing structure; a swing sensor that senses a swing of the swing structure; a travel sensor that senses travelling of the track structure; and a controller that computes an orientation of the track structure, and a horizontal coordinate of the blade.

Abstract: In a hydraulic excavator including a track structure, a swing structure swingably disposed on an upper portion of the track structure, a work implement coupled to the swing structure, an earth removal device including a blade coupled to the track structure and a lift cylinder configured to raise and lower the blade, an operation sensor configured to detect an operation of a travelling lever, a height sensor configured to measure a height of the blade with respect to the track structure, an antenna for a satellite positioning system, the antenna being mounted on the swing structure, and a controller configured to calculate positional data regarding the blade, the controller is configured to determine a travelling operation on the basis of a signal of the operation sensor, calculate a travelling direction of straight forward travelling of the track structure as an orientation of the track structure when the straight forward travelling of the track structure is detected from a trajectory of the antenna with a st

Abstract: To provide a work machine having a blade provided to a track structure, and a swing structure provided swingably on the upper side of the track structure, which work machine allows for computation of the horizontal coordinates of the blade. The work machine includes: a swing-structure-position acquiring device that acquires a horizontal coordinate and an orientation of the swing structure; a swing sensor that senses a swing of the swing structure; a travel sensor that senses travelling of the track structure; and a controller that computes an orientation of the track structure, and a horizontal coordinate of the blade.

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.

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.

Abstract: An actuator lock switching valve 50 is provided which communicates a drain line 52 and a pilot line 53 with each other when the valve 50 is in a position C, and which communicates pilot lines 51, 53 with each other when it is shifted to a position D. The pilot line 51 is connected to a delivery line 7 of a hydraulic pump 10, and the pilot line 53 is connected to pressure receiving sections 28a, 28b provided at ends of the pressure compensating valves 21a, 21b on the side acting in the closing direction. The actuator lock switching valve 50 has a pressure receiving section 55 connected to the output side of a pilot lock switching valve 43, and is switched over in interlock with shifting of the switching valve 43.

Abstract: An actuator lock switching valve 50 is provided which communicates a drain line 52 and a pilot line 53 with each other when the valve 50 is in a position C, and which communicates pilot lines 51, 53 with each other when it is shifted to a position D. The pilot line 51 is connected to a delivery line 7 of a hydraulic pump 10, and the pilot line 53 is connected to pressure receiving sections 28a, 28b provided at ends of the pressure compensating valves 21a, 21b on the side acting in the closing direction. The actuator lock switching valve 50 has a pressure receiving section 55 connected to the output side of a pilot lock switching valve 43, and is switched over in interlock with shifting of the switching valve 43.

Abstract: A hydraulic drive system includes a pump control unit 18 for controlling a pump delivery rate such that a pump delivery pressure is held at a predetermined value higher than a maximum load pressure among actuators 2-6. Pressure compensating valves 12-16 are each constructed to set, as a target compensation differential pressure, a differential pressure between the delivery pressure of a hydraulic pump 1 and the maximum load pressure among the actuators 2-6. The pressure compensating valve 12 is given such a load dependent characteristic that the target compensation differential pressure is reduced when a load pressure rises. A lower limit setting spring 55 for limiting the target compensation differential pressure from becoming smaller than a predetermined value is provided in the pressure compensating valve 12 for the swing section.

Abstract: An engine speed control system for a construction machine is arranged in association with its hydraulic circuit, which has main pumps, a communication line through which input ports of travel-controlling directional control valves are connected with each other, and a travel-controlling communication valve arranged in the communication line.