Abstract: A floor support frame (8) is provided with a left side pilot valve (21). The left side pilot valve (21) is provided with a left side operating pedal (23) that is foot-operated. The left side operating pedal (23) is configured of a first foot board (26) that is mounted on the left pilot valve (21) to be rotatable in an upper-lower direction, a shaft (27) that is mounted in a rear portion of the first foot board (26), and a second foot board (28) that is mounted through the shaft (27) on the first foot board (26) to be rotatable in a horizontal direction. The second foot board (28) is rotatable between a storage position of overlapping the first foot board (26) and a use position of being rotated in the rear side of the first foot board (26). An operation regulating mechanism (29) is provided in the front side of the first foot board (26) to be engaged to the second foot board (28) when the second foot board (28) is rotated to the storage position to regulate a foot operation.

Abstract: A hydraulic excavator (1) includes a wireless authentication device (42) performing wireless authentication with a portable key device (41) and a vehicle body controller (39) allowing or prohibiting start of the engine (15) on the basis of authentication by the wireless authentication device (42) and an operation of a power switch (12). The wireless authentication device (42) transmits a request signal within an authenticable range and performs authentication when it receives an ID code for authentication replied from the portable key device (41) on the basis of the transmitted request signal. The vehicle body controller (39) allows start of the engine (15) by the power switch (12) when a gate lock lever (13) is switched to a lock position and the wireless authentication device (42) performs authentication by the portable key device (41).

Abstract: It is an object of the present invention to accurately detect the absorption torque of the other of two hydraulic pumps by a purely hydraulic structure and feed the absorption torque to one of the two hydraulic pumps, thereby to accurately perform a total torque control, effectively utilize a rated output torque of a prime mover, and enhance mountability.

Abstract: An object to achieve favorable operability, in a combined operation that involves a specific actuator and involves a great difference in load pressure and when an operation of an operating unit for the specific actuator is a fine operation, by reducing energy consumption arising from wasted restricting pressure loss of a pressure compensating valve and by flexibly varying a flow rate of a hydraulic fluid supplied to the specific actuator depending on the load pressure. To achieve this object, a boom cylinder (3a) is provided with an open center type flow control valve (6a) that controls a hydraulic fluid from a main pump (202) and a closed center type flow control valve (6i) that controls a hydraulic fluid from a main pump (102). The main pump (102) is subject to load sensing control. The flow control valve (6a) is opened to control a supply flow rate up to an intermediate zone of an operating range of an operating unit for the boom cylinder (3a).

Abstract: A bucket cylinder includes a cylindrical tube, a rod having a cylindrical boss part mounted to a protruding end side of the rod, and a protective cover having one side supported by a cover guide provided on the tube, while the other side is mounted on the boss part. A protective protrusion protruding outward in a radial direction of the boss part and protecting the boss part and the protective cover is provided on the boss part. The protective cover is formed having a plate shape by a material having elasticity, and the protective cover includes a plate part for protecting the rod between the cover guide and the boss part and a winding part formed so as to be wound around an outer periphery of the boss part from a distal end side of the plate part. A protective protrusion engaging hole into which the protective protrusion is engaged is provided in the winding part at a position corresponding to the protective protrusion.

Abstract: In addition to a main pump 102 having two delivery ports 102a and 102b and performing the load sensing control, two subsidiary pumps 202 and 302 for the load sensing control for respectively performing assist driving on a boom cylinder 3a and an arm cylinder 3b are provided. When driving the boom cylinder 3a or the arm cylinder 3b, a selector valve 141 or 241 is switched and flows of hydraulic fluid are merged together and supplied to the boom cylinder 3a or the arm cylinder 3b. When driving actuators other than the boom cylinder 3a or the arm cylinder 3b, only the hydraulic fluid from the main pump is supplied to the actuators. In short, the hydraulic drive system is configured so that two specific actuators having great demanded flow rates and tending to have a great load pressure difference between each other when driving at the same time can be driven with hydraulic fluid delivered from separate delivery ports.

Abstract: Provided is an electric construction machine adapted to prevent an electric current, after flowing in via a junction at which power transmission systems join together, from flowing into at least one connector to which an external power supply is not connected. Power transmission systems 71A, 71B, 71C connected to connectors 59A, 59B, 59C are all caused to join with a common system 73 at a junction before being connected to a control unit 35. The power transmission systems 71A, 71B, and 71C include switches 74Aa, 74Ab, 74Ba, 74Bb, 74Ca, 74Cb.

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: An object of the invention is to achieve a travel speed known in the art during travelling operation, improve energy efficiency by reducing energy loss, and obtain favorable travel operability less susceptible to effects from variations in a travel load and changes in a pump delivery pressure when travelling operation is performed through operation of a travel lever over a half stroke range or less. A variable restrictor valve 80 is disposed in parallel with a flow sensing valve 50 of an engine speed sensing valve unit 13. A travel pilot pressure is adapted to act in an opening direction of the variable restrictor valve 80. The variable restrictor valve 80 is set to have a continuously increasing opening area from a full closure to a maximum with an increasing travel pilot pressure.

Abstract: Control valves 100f, 100g, and 100h that reduce flow passage areas of parallel hydraulic fluid lines 41f, 41g, and 41h respectively when operating devices 34a, 34b for traveling are operated, are each disposed in the parallel hydraulic fluid line 41f, 41g, or 41h so that if saturation occurs during combined operations control likely to generate a significant difference in load pressure between any two actuators, the control valve prevents full closing of a pressure compensating valve lower in load pressure and thus prevents a slowdown and stop of the actuator undergoing the lower load pressure, and so that if saturation occurs during combined operations control likely to generate a particularly significant difference in load pressure between any two actuators, the control valve ensures a necessary supply of hydraulic fluid to the actuator higher in load pressure, thereby preventing a slowdown and stop of the actuator higher in load pressure.

Abstract: Pressure sensors are provided to detect the delivery pressure of a hydraulic pump, the output pressure of an engine revolution speed detecting valve, and the output pressure of a differential pressure reducing valve generating the differential pressure between the delivery pressure of the hydraulic pump and a maximum load pressure. A vehicle controller calculates virtually the displacement of the hydraulic pump by use of the detected pressures and an equation of motion about a swash plate of the hydraulic pump, calculates the power need of the hydraulic pump and the output of the engine using these values, and switches a motor between powering and generation control in accordance with the result of a comparison between the pump power need and the engine output. In this manner, the displacement of the hydraulic pump without using sensors to detect the tilting angle of the swash plate of the hydraulic pump.

Abstract: During an operation, a control device (38) for performing output control of an engine (10) determines whether or not the engine (10) and/or an exhaust gas purifying device (18) has a malfunction. If it is determined that the engine (10) and/or the exhaust gas purifying device (18) has a malfunction, a highest rotational speed of the engine (10) is controlled to a second rotational speed (Nt) higher by a predetermined amount (?) than a first rotational speed (Ns) at which an engine maximum torque (Tm) before the malfunction can be outputted. In this case, a maximum fuel injection quantity of the engine (10) is limited so that a rated torque (Tr) before the malfunction can be outputted at the first rotational speed (Ns).