Abstract: The invention provides a controller of an engine and a variable capacity pump which can perform a speedy work even under a heavy load and a strong work at the critical moment. Accordingly, there is provided control means (30) which outputs commands to a fuel injection pump (2), relief control means (19, 21) and variable capacity pump output control means (27, 29) so that when a signal for an on operation of an active mode switch (7) is inputted, the product of a pump discharge pressure P by a pump discharge amount Q is expressed by a P-Q constant horsepower curve Ha in an active mode in which the product of P and Q is higher than a predetermined value in the normal operation, and when a signal for an on operation of a power mode switch (9) is inputted, the product of the pump discharge pressure P by the pump discharge amount Q is expressed by a P-Q constant horsepower curve Hap in a power active mode in which the product of P and Q is higher than that in the active mode by one stage.

Abstract: A controller, for a variable capacity pump, prevents engine stalls due to rapid changes in operating load by increasing the pump absorption torque when the engine speed is high so as to increase the work amount and by reducing the pump absorption torque when the engine speed is low. The controller receives a signal from an engine speed sensor for detecting engine speed. A pump absorption torque curve is pre-set so as to be consecutively stepped with respect to engine speed so as to intersect at an engine rated point. The pump absorption torque is then calculated in accordance with increases or decreases in engine speed. The pump absorption torque is then set to prescribe values based on the results of these calculations and an instruction is outputted to a control valve in such a manner as to regulate a regulator of the variable capacity pump.

Abstract: A control circuit for a piece of heavy machinery reduces a speed of one actuator, having a lower load, when that actuator and another actuator, having a higher load, are operated simultaneously. The control circuit includes a first control valve for supplying a first actuator with pressurized oil, discharged from a hydraulic pump; a second control valve for supplying a second actuator with pressurized oil, discharged from the hydraulic pump; operating units for actuating the first control valve and the second control valve; and a mode selector for providing a command to the second control valve in order to increase a speed of the first actuator compared with that of the second actuator when the first and second actuators are operated simultaneously. A variable adjustor can be provided to control the open area of a valve for enabling the stroke of the spool of the second control valve to regulated.

Abstract: This invention aims to improve the operability in a hydraulic drive machine. According to a load Pp on work machine actuators 3 and 4, a differential pressure of a discharge pressure Pp of a hydraulic pump and a load pressure PLS is varied. Further, the differential pressure is varied so that the differential pressure between the discharge pressure Pp of the hydraulic pump 2 and the load pressure PLS decreases as the load Pp on the work machine actuators 3 and 4 increases and a rotational speed .epsilon.E of an engine decreases. Furthermore, the rotational speed .epsilon.E of the engine 1, discharge pressure Pp of the hydraulic pump 2, the operation amounts S1 and S2 of the various operation levers are detected, respectively, the absorbing torque of the hydraulic pump 2 is set based on the detected rotational speed .epsilon.E and a target rotational speed .epsilon.

Abstract: A control device for hydraulically operated machines for carrying out control to move a working unit with priority over other working units. A weight is added to each of the same manipulated amount of a plurality of operation levers 3, 4 in association with work type of M1 to M5 and the weights are stored in a memory of a controller 5 in association with the type of the operation levers 3, 4 and the work type. The work type M1 to M5 are selected by a switch 2. When the operation lever 3, 4 is manipulated and a work type is selected by the switch 2, the weight associated with the type of the manipulated operation lever 3, 4 and the selected work type M1 to M2 is read from the memory, and the read weight is added to a manipulated amount S1, S2 of the manipulated operation lever 3, 4. Then, not signals indicative of the manipulated amount S1, S2 of the operation lever 3, 4 but signals E, E' added with the weight which are indicative of the manipulated amount are outputted to control valves 7.

Abstract: A hydraulic oil volume change-over control apparatus for a hydraulic excavator subjects a hydraulic pump to load sensing control so as to set an optimum volume of hydraulic oil while an engine for driving the hydraulic pump is operated at a rotational speed at which the fuel consumption of the engine is minimum, by setting a low power mode during breaker work or the like which is performed with a smaller volume of hydraulic oil than that needed during normal excavating work.

Abstract: A hydraulic excavator adapted to be changed over simply to a fine operation mode so as to control the capacity of a hydraulic pump through load-sensing control to thereby make it possible to perform accurate work when the machine needs to be finely operated temporarily for operations such as ground levelling, and position adjustment on a dump vessel, wherein the fine operation mode is easily cleared to switch the excavator to a standard mode to thereby improve operability, as well as work efficiency. When the excavator is switched to the fine operation mode so as to control the capacity of the hydraulic pump through load-sensing control for accurate work, the engine is driven at such a torque and engine revolution as permitting a minimum fuel consumption, thus reducing the fuel consumption of the engine.

Abstract: Hydraulically-operated equipment such as travelling equipment or working equipment for use in construction machinery such as a power shovel, shoveldozer and bulldozer. The hydraulically-operated equipment comprises a hydraulic driving mechanism actuated by hydraulic pressure, a hydraulic pressure supplying device for supplying hydraulic pressure to a hydraulic pipeline system for the hydraulic driving mechanism and a controller for controlling the hydraulic pressure supplying device such that the supplying rate at which hydraulic pressure is supplied to the hydraulic pipeline system according to the supply of hydraulic pressure is decreased in a specified period after a dead zone period in which hydraulic pressure starts to rise. This arrangement prevents an operational lag in the hydraulic driving mechanism as well as a shock at the time of start-up and shut-down.

Abstract: An operator's actions for achieving a desired operation of a machine's actuator can be memorized in a teaching mode and the memorized information can be used for automatically reproducing the desired operation in a play back mode, to alleviate the operator's burden. A failure in the play back mode caused by the difference in the conditions under which the play back mode and the teaching mode are conducted can be eliminated, and the operation can be allowed to be continued in the manual mode even if a failure occurs in an automated operation control system. In order to achieve these, when a correction operation by the operator is detected in the play back mode, the play back mode is interrupted and the correction operation is processed with priority to the play back operation.

Abstract: In a hydraulic drilling machine with a boom, arm and bucket as working parts, one or more of the working parts can be vibrated automatically to perform effective drilling with reduced resistance in various types of operations when the soil changes. Adequate vibration can be automatically generated by setting the working mode (Bo, A, Bu, Sk) and vibration mode (L, M, S) according to the soil or operation form beforehand and by setting the automatic vibration mode. Furthermore, since the control input of the working part lever can be added to the automatic vibration, simple and minute repeated operations, such as pressure-shifting, sifting or drilling conducted while the bucket is vibrated, can be performed readily and uniformly without exhausting the operator, and workability can thus be greatly improved.

Abstract: A teaching and playback method for a work machine that is applicable to construction equipment such as a hydraulic excavator to automatize operation. Data on the operator's operation of work machine actuators is stored, and the stored data is reproduced so that the same operation as that by the operator is automatically performed. The method is adapted to effect exactly the same operation as what has been taught even when, during playback, the load on the actuators has varied from the level applied during the teaching. For this purpose, the pump discharge amount and the amounts of flow supplied to the actuators which are present during the teaching are stored. During playback, when the load has varied, and the pump discharge has changed, the engine output is controlled in such a manner that the actual pump discharge becomes equal to the amount stored during the teaching.

Abstract: A service valve circuit of a hydraulic excavator connected beforehand for use in controlling a special attachment in addition to a prescribed actuator control valve. The service valve circuit comprises a confluence valve 17 for performing electromagnetic proportional flow rate control, disposed in a confluence circuit 16 in communication with the section between inflow circuits 3F and 3R of two variable pumps 2F and 2R, an electrical switch 21 for switching the confluence valve 17 on or off according to a required flow rate and a volume 22 for adjusting the quantity of flow after passing through a confluence valve 17 in a range of flow for a maximum of one to two pumps. Since the requirement of confluence with respect to a required quantity of flow for a special attachment e and the quantity of confluence are set in advance, there will be no excess or shortage of the quantity of confluence.