Abstract: An antitheft system can be provided by constructing such that, when a stop signal has been inputted from an engine 7, a main controller 2 outputs, until a first predetermined time Ts elapses, a turn-on signal to switches 8, 9 to perform a similar antitheft processing as in an operation of the engine 7 and after an elapse of the first predetermined time Ts, instructs the switch 9 to repeat a turn-on and turn-off at predetermined time intervals ?t, and, whenever the switch 9 is brought into a turned-on position, detects a position at that time by a position detecting controller 3 and compares the position with a position at the time of an engine stop to determine whether or not a theft has taken place. Owing to this construction, it is no longer necessary to always feed power to the position detecting controller 3 during the stop of the engine 7, thereby making it possible to cut down the feeding of as much power to the controller 3 as a time elapsed during which the switch 9 is kept off.

Abstract: To permit using hold-side pressure oil in a first hydraulic cylinder for the acceleration of a second hydraulic cylinder upon performing a combined operation of the first and second hydraulic cylinders, a hydraulic drive system is provided with a main hydraulic pump 21, a boom cylinder 6 and an arm cylinder 7, a directional control valve 23 for a boom and a directional control valve 24 for an arm, and a boom control device 25 and an arm control device 26. The hydraulic drive system is also provided with a pressure oil feed means for feeding pressure oil in a rod chamber 6b of the boom cylinder 6 to an upstream side of the directional control valve 24 for the arm when a bottom pressure of the arm cylinder 7 has increased to a high pressure equal to or higher than a predetermined pressure. This pressure oil feed means includes a flow combiner valve 44 arranged in a reservoir line 42 which can communicate to the rod chamber 6b of the boom cylinder 6.

Abstract: A modification torque ?T and a torque converter speed ratio e is computed from input and output revolution speeds of a torque converter 31. A first determination coefficient ? corresponding to the speed ratio e, and a second determination coefficient ? corresponding to a pump pressure are computed. A selector 87 selects the smaller one of these coefficients as a determination coefficient ?, and the modification torque ?T is multiplied by ? to provide a modification torque ?TA. An adder 89 adds the modification torque ?TA (negative value) to a pump base torque TR to provide a modified pump base torque TRA, whereby a maximum pump absorption torque TRA is controlled so as to become TRA. The maximum pump torque reducing control can then be performed while accurately confirming a work situation during the combined operation of travel and a working actuator.

Abstract: A maintenance system of a hydraulic excavator (11) is provided with a maintenance monitoring device (21), a maintenance management server (12) for managing trouble information and operating information for each working machine, a model information server (13), and a service personnel mobile terminal (14) connected to one another through the Internet (15). When trouble occurs in the hydraulic excavator, the maintenance system (21) transmits trouble information to the maintenance management server (12), and the maintenance management server (12) transmits information on occurrence of trouble to the mobile terminal (14) and displays it on a display unit. This system manages the maintenance manuals and other data for each model in a model information database separate from the maintenance database and correlates the two databases based on the model data.

Abstract: To keep one of three hydraulic pumps unaffected by variations in torque of the remaining hydraulic pumps when the three hydraulic pumps are used, displacements of the first and second hydraulic pumps are controlled based on their own delivery pressures P1,P2 and a pressure P3? obtained by reducing through a reducing valve 14 a delivery pressure P3 from the third hydraulic pump, while a displacement of the third hydraulic pump 3 is controlled only by its own delivery pressure P3. The pressure oil delivered from the third hydraulic pump 3, therefore, remains unaffected by variations in delivery flow rates from the first and second hydraulic pumps 1,2, in other words, by variations in their torque consumptions, so that the third hydraulic pump is assured to provide a stable flow rate.

Abstract: Assessment information needed to calculate a used vehicle assessment value of a hydraulic excavator 10 is input to a portable telephone 20 and is then transmitted from the portable telephone 20. The transmitted assessment information is received at a manufacturer's base station 40 at a remote location. The used vehicle assessment value of the hydraulic excavator 10 is calculated based upon the received assessment information, and history information and operation information on the hydraulic excavator 10 read out from an operation information database 43 and a history database 42 in correspondence to an ID number assigned to the hydraulic excavator which is included in the assessment information.

Abstract: A display device for a construction machine has a display switching means, output control means, operation detecting means, and display prohibiting means. The display switching means switches information displayed on a monitor placed in an operation cabin, where the switching is made to prevent display of unnecessary information on the monitor while the construction machine is performing work. The output control means selects display information recorded in information recording means and outputs the selected information to the monitor. The operation detecting means detects whether or not the construction machine is in a working state. When the operation detecting means detects that the construction machine is in the working state, display switching operation of the monitor is performed by the display switching means, and the display prohibiting means prohibits the display of specific information.

Abstract: Assessment information needed to calculate a used vehicle assessment value of a hydraulic excavator 10 is input to a portable telephone 20 and is then transmitted from the portable telephone 20. The transmitted assessment information is received at a manufacturer's base station 40 at a remote location. The used vehicle assessment value of the hydraulic excavator 10 is calculated based upon the received assessment information, and history information and operation information on the hydraulic excavator 10 read out from an operation information database 43 and a history database 42 in correspondence to an ID number assigned to the hydraulic excavator which is included in the assessment information.

Abstract: A working machine maintenance system having a plurality of working machines. A center server is provided that manages maintenance on the plurality of working machines by engaging in data exchange through bidirectional communication with each of the plurality of working machines via a communication line. The working machines each include an operation data storage device, an operation device operated to enter a maintenance work completion, a data transmission device, a data reception device, and a display device at which the maintenance information is displayed. The center server includes a data reception device that receives the operation data, the maintenance work completion data, and the maintenance data that have been transmitted, an operation database in which the operation data are stored, a maintenance database, a calculation device that calculates maintenance timing. and a data transmission device that transmits data related to the maintenance information.

Abstract: To permit using hold-side pressure oil in a first hydraulic cylinder for the acceleration of a second hydraulic cylinder upon performing a combined operation of the first and second hydraulic cylinders, a hydraulic drive system is provided with a main hydraulic pump 21, a boom cylinder 6 and an arm cylinder 7, a directional control valve 23 for a boom and a directional control valve 24 for an arm, and a boom control device 25 and an arm control device 26. The hydraulic drive system is also provided with a pressure oil feed means for feeding pressure oil in a rod chamber 6b of the boom cylinder 6 to an upstream side of the directional control valve 24 for the arm when a bottom pressure of the arm cylinder 7 has increased to a high pressure equal to or higher than a predetermined pressure. This pressure oil feed means includes a flow combiner valve 44 arranged in a reservoir line 42 which can communicate to the rod chamber 6b of the boom cylinder 6.

Abstract: Provided is a communication system for working machines, which makes it possible to transmit desired messages from sites, where the working machines are arranged, to their corresponding work administration centers at timings as needed. When a mail switch 10 arranged on a working machine 7 is operated to send information to a server 1, a terminal user-company identification unit 14 identifies, on the basis of a terminal information database 18, a user to which the information so received is to be sent. A user-company-dependent mail selection unit 15 selects customer information 19a on the user from a customer database 19. At a transmission mail creation unit 16, a corresponding new message 16a is created. The mail is then transmitted from a mail output unit 17. In this manner, a desired message can be sent from each working machine 7 at a remote location to the corresponding user at a timing as needed.

Abstract: Construction machine management, permitting operation of a construction machine only under specified conditions and inhibiting its operation in case it is in a state incongruent with preset working conditions. Working conditions for each construction machine are set up by a working conditions setup means, including a geographically divided working area and a working time zone in which a construction machine is allowed to operate in a specified working area. Setup working conditions are stored in a memory means. At the time of starting a construction machine, the status of the construction machine is checked for by a status checkup means which is adapted to check for current position of the construction machine and current time against the working area and working time zone of the setup working conditions.

Abstract: A joining directional control valve 13 is disposed to supply, to an arm cylinder 4, not only a hydraulic fluid delivered from a first hydraulic pump 1, but also a hydraulic fluid delivered from a second hydraulic pump 2 when an arm directional control valve 14 is driven. Respective delivery pressures of the hydraulic pumps 1, 2 are detected by pressure sensors 101, 102, and the opening area of a recovery control valve 6 is controlled depending on a lower one of the detected pressures from the pressure sensors 101, 102 such that, even in the combined operation of the arm cylinder 4 and another actuator 3, 4, the hydraulic fluid can be recovered for return to the arm cylinder 4 when the load pressure of the arm cylinder 4 is low. Thus, by supplying the hydraulic fluids from the two hydraulic pumps to the particular actuator for which the hydraulic fluid is to be recovered, a recovery flow rate is ensured when the load of the particular actuator is low in the combined operation.

Abstract: To keep one of three hydraulic pumps unaffected by variations in torque of the remaining hydraulic pumps when the three hydraulic pumps are used, displacements of the first and second hydraulic pumps are controlled based on their own delivery pressures P1,P2 and a pressure P3? obtained by reducing through a reducing valve 14 a delivery pressure P3 from the third hydraulic pump, while a displacement of the third hydraulic pump 3 is controlled only by its own delivery pressure P3. The pressure oil delivered from the third hydraulic pump 3, therefore, remains unaffected by variations in delivery flow rates from the first and second hydraulic pumps 1,2, in other words, by variations in their torque consumptions, so that the third hydraulic pump is assured to provide a stable flow rate.

Abstract: A modification torque computing unit 83 computes a modification torque ?T and a torque converter speed ratio e is computed from input and output revolution speeds of a torque converter 31. A first determination coefficient ? corresponding to the speed ratio e, and a second determination coefficient ? corresponding to a pump pressure are computed. A selector 87 selects the smaller one of these coefficients as a determination coefficient ?, and the modification torque ?T is multiplied by ? to provide a modification torque ?TA. An adder 89 adds the modification torque ?TA (negative value) to a pump base torque TR to provide a modified pump base torque TRA, whereby a maximum pump absorption torque TRA is controlled so as to become TRA. The maximum pump torque reducing control can then be performed while accurately confirming a work situation during the combined operation of travel and a working actuator.

Abstract: To keep one of three hydraulic pumps unaffected by variations in torque of the remaining hydraulic pumps when the three hydraulic pumps are used, displacements of the first and second hydraulic pumps are controlled based on their own delivery pressures P1, P2 and a pressure P3? obtained by reducing through a reducing valve 14 a delivery pressure P3 from the third hydraulic pump, while a displacement of the third hydraulic pump 3 is controlled only by its own delivery pressure P3. The pressure oil delivered from the third hydraulic pump 3, therefore, remains unaffected by variations in delivery flow rates from the first and second hydraulic pumps 1,2, in other words, by variations in their torque consumptions, so that the third hydraulic pump is assured to provide a stable flow rate.

Abstract: A working machine failure diagnosis method for performing a failure diagnosis by transmitting and receiving signals through communication devices provided at a working machine and at an information management center, according to the present invention, includes: a first step in which a first signal related to a failure of the working machine is generated at the working machine and the first signal is transmitted to the information management center from the working machine via the communication devices; a second step in which, after the first signal is transmitted, the information management center generates a second signal for identifying a location of the failure based upon the first signal and the second signal is then transmitted from the information management center to the working machine via the communication devices; and a third step in which failure information corresponding to the first signal and the second signal is provided to an operator.

Abstract: A traveling hydraulic working machine has input means for commanding a target revolution speed of an engine and detection means for detecting an operating situation of a hydraulic actuator and an operating situation of traveling means. A prime-mover revolution speed control means modifies the target revolution speed of the prime mover when the operating situation of the hydraulic actuator and the operating situation of the traveling means come into respective particular states, and controls the revolution speed of the prime mover. With the traveling hydraulic working machine, in the combined operation of traveling and working a hydraulic actuator, work can be performed on the basis of the engine revolution speed intended by an operator. When a working load varies, the engine revolution speed is automatically controlled.

Abstract: An antitheft system can be provided by constructing such that, when a stop signal has been inputted from an engine 7, a main controller 2 outputs, until a first predetermined time Ts elapses, a turn-on signal to switches 8, 9 to perform a similar antitheft processing as in an operation of the engine 7 and after an elapse of the first predetermined time Ts, instructs the switch 9 to repeat a turn-on and turn-off at predetermined time intervals ?t, and, whenever the switch 9 is brought into a turned-on position, detects a position at that time by a position detecting controller 3 and compares the position with a position at the time of an engine stop to determine whether or not a theft has taken place. Owing to this construction, it is no longer necessary to always feed power to the position detecting controller 3 during the stop of the engine 7, thereby making it possible to cut down the feeding of as much power to the controller 3 as a time elapsed during which the switch 9 is kept off.

Abstract: The present invention is applied to a system comprised of large number of hydraulic excavators 1 deployed at construction sites and a base station 16. Each hydraulic excavator 1 is provided with a storage unit (memory 402), a control unit (CPU 401) for executing the work operation and receiving as input a quantitative machine status relating to the work operation, and a communications device 42. The base station 16 is provided with a communications device 16a, a management server 17 for identifying the serial number of the hydraulic excavator 1 and transferring information, and a database 18 for storing various information. The control unit of the hydraulic excavator 1 and the management server 17 of the base station 16 transfer information.