Abstract: In a control device for construction machinery, a system operating point calculation unit calculates a plurality of combinations of engine rotational speed and engine torque with which demanded power of an engine can be generated; and calculates system efficiency in each of the combinations according to discharge pressure of a hydraulic. A rotational speed calculation unit calculates target rotational speed of the engine as the engine rotational speed in one of the combinations of the engine rotational speed, the engine torque and the system efficiency calculated by the system operating point calculation unit that includes desired system efficiency. A displacement calculation unit calculates target displacement of the hydraulic pump based on the target rotational speed calculated by the rotational speed calculation unit and demanded flow rate of the hydraulic pump. With this control device, the engine and the hydraulic pump can be controlled at an efficient operating point.

Abstract: A hydraulic working machine has an assist electric motor connected to an engine and a hydraulic pump. The emissions of air pollutants in the exhaust gas from the engine are minimized regardless of fluctuations in the load torque of the hydraulic pump. A specific revolution speed suitable for reducing the emissions of air pollutants is stored, and an engine is controlled using the specific revolution speed as a target revolution speed. The absorption torque of a hydraulic pump is subjected to high-pass filtering whereby a high-frequency component devoid of a trend component is obtained. Target assist torque is computed from the high-frequency component, and the assist electric motor is subjected to power running/generation control accordingly. A specific output torque range suitable for reducing the emissions of air pollutants is stored, and the target assist torque is corrected so that the trend component does not exceed the specific output torque range.

Abstract: To automatically prevent a reverse movement by inhibiting an excessive increase in an output torque of an electric motor. A means (31) calculates a target value for a rotation speed based on a command from a system (20), a means (32) calculates a deviation between a detection value from a rotation speed sensor (81) and the target value, a means (33) calculates a first target torque in a direction that the deviation will be eliminated, and a means (34) calculates, based on a command from the system (20), a second target torque in the same direction as the target value. A means (50) calculates a variation in a rotation angle of an electric motor (12) in a first range, and a means (60) calculates the same variation in a second range.

Abstract: In a hybrid construction machine, there is provided a drive control device which realizes in, as a simple a structure as possible, control means of a motor generator, which is capable of preventing rapid decreases in the state of charge. The control means, which calculates a motor torque command value to be output to the motor generator, is characterized by calculating the motor torque command value, based on a difference between an actual state-of-charge and a prescribed target state-of-charge and a torque margin obtained by a difference between a maximum torque of an engine determined based on an actual rotational speed of the engine and an actual torque of the engine.

Abstract: In a control device for construction machinery, a system operating point calculation unit calculates a plurality of combinations of engine rotational speed and engine torque with which demanded power of an engine can be generated; and calculates system efficiency in each of the combinations according to discharge pressure of a hydraulic. A rotational speed calculation unit calculates target rotational speed of the engine as the engine rotational speed in one of the combinations of the engine rotational speed, the engine torque and the system efficiency calculated by the system operating point calculation unit that includes desired system efficiency. A displacement calculation unit calculates target displacement of the hydraulic pump based on the target rotational speed calculated by the rotational speed calculation unit and demanded flow rate of the hydraulic pump. With this control device, the engine and the hydraulic pump can be controlled at an efficient operating point.

Abstract: A motive power regeneration apparatus for a working machine includes a regeneration circuit that is connected to a hydraulic line through which a returning fluid of a boom cylinder is distributed during a boom lowering operation. Also included are a hydraulic motor connected to a generator, a flow regulating circuit that is connected to the hydraulic line and provided with a control valve, an inverter that controls the flow rate on the regeneration circuit in accordance with a first flow rate setting which varies with the operation amount of an operating apparatus, and a control valve and a proportional valve that control the flow rate on the flow regulating circuit in accordance with a second flow rate setting which varies with the operation amount of the operating apparatus. Therefore, the motive power regeneration apparatus is capable of making an operator constantly feel comfortable with the working machine operations.

Abstract: A hydraulic working machine has an assist electric motor connected to an engine and a hydraulic pump. The emissions of air pollutants in the exhaust gas from the engine are minimized regardless of fluctuations in the load torque of the hydraulic pump. A specific revolution speed suitable for reducing the emissions of air pollutants is stored, and an engine is controlled using the specific revolution speed as a target revolution speed. The absorption torque of a hydraulic pump is subjected to high-pass filtering whereby a high-frequency component devoid of a trend component is obtained. Target assist torque is computed from the high-frequency component, and the assist electric motor is subjected to power running/generation control accordingly. A specific output torque range suitable for reducing the emissions of air pollutants is stored, and the target assist torque is corrected so that the trend component does not exceed the specific output torque range.

Abstract: A motive power regeneration apparatus for a working machine includes a regeneration circuit that is connected to a hydraulic line through which a returning fluid of a boom cylinder is distributed during a boom lowering operation. Also included are a hydraulic motor connected to a generator, a flow regulating circuit that is connected to the hydraulic line and provided with a control valve, an inverter that controls the flow rate on the regeneration circuit in accordance with a first flow rate setting which varies with the operation amount of an operating apparatus, and a control valve and a proportional valve that control the flow rate on the flow regulating circuit in accordance with a second flow rate setting which varies with the operation amount of the operating apparatus. Therefore, the motive power regeneration apparatus is capable of making an operator constantly feel comfortable with the working machine operations.

Abstract: In a hybrid construction machine, there is provided a drive control device which realizes in, as a simple a structure as possible, control means of a motor generator, which is capable of preventing rapid decreases in the state of charge. The control means, which calculates a motor torque command value to be output to the motor generator, is characterized by calculating the motor torque command value, based on a difference between an actual state-of-charge and a prescribed target state-of-charge and a torque margin obtained by a difference between a maximum torque of an engine determined based on an actual rotational speed of the engine and an actual torque of the engine.

Abstract: A speed command value X1 for a first arm 3 is decided depending on a lever input amount in the direction c, d. Assuming that the side d corresponding to move-up of the first arm is positive, the side c corresponding to move-down thereof is negative, and a speed command value resulted upon full lever operation and corresponding to a rated speed of the first arm is 1, X1 is given by -1<X1<1. A speed command value X3 for a third arm 5 is decided depending on a lever input amount in the direction e, f. Assuming that the side f corresponding to dumping of the third arm is positive, the side e corresponding to crowding thereof is negative, and a speed command value resulted upon full lever operation and corresponding to a rated speed of the third arm is 1, X3 is given by -1<X3<1. A speed command value X2 for a second arm 4 is here given by X2=K1.times.X1+K3.times.X3 on condition that the side corresponding to move-up of the second arm is positive.

Abstract: Two control lever units 11, 12 for operating a first arm 3, a second arm 4 and a third arm 5 of a 3-articulation work front 2 are provided, and signals 132, 133 from the two control lever units are sent to a controller 131. On condition that a virtual 2-articulation type work front comprising a virtual first arm 13 and a virtual second arm 14 is imaginarily provided and the relationship in movement between the virtual second arm and the actual third arm is set in advance as if both the arms constitute a rigid body together, the controller 131 determines respective command values .omega..sub.1, .omega..sub.2 and .omega..sub.

Abstract: A first hydraulic circuit comprises a variable displacement hydraulic pump driven by a prime mover, a variable displacement hydraulic motor connected in a closed circuit to the variable displacement hydraulic pump, and a displacement control means for controlling a displacement of the variable displacement hydraulic motor. A second hydraulic circuit comprises a hydraulic pump driven by the prime mover, and drives a loader attachment. A displacement limitation means limits the maximum value of the displacement of the variable displacement hydraulic motor in accordance with a load pressure of the second hydraulic circuit. For example, the displacement limitation means reduces the maximum value of the displacement of the variable displacement hydraulic motor in proportion to the pressure in the second hydraulic circuit. The motor torque is controlled by directly adjusting the displacement of the motor, and a load of the hydraulic motor can thus be stably controlled.

Abstract: A hydraulic drive system is equipped with an engine, a plurality of hydraulic pumps adapted to be driven by the engine and including a variable displacement hydraulic pump provided with a displacement varying mechanism, a hydraulic motor connected to the variable displacement pump, a hydraulic actuator for actuating the displacement varying mechanism of the variable displacement hydraulic pump, a working fluid feeding means for feeding the hydraulic actuator with a hydraulic fluid of a pressure according to the degree of control of an accelerator lever which is adapted to instruct a target revolution number of the engine, and a low-pressure circuit for allowing the hydraulic fluid to be discharged therethrough from the hydraulic actuator.

Abstract: A hydraulic drive circuit system is equipped with an accelerator pedal and an accelerator lever for respectively instructing target revolution numbers for an engine, a link plate for selecting greater one of the instruction values, and a linkage and a switch for controlling valves respectively so as to close the flow passage of a line interposed between a charge pump and a low pressure line irrespective of the instruction value of the accelerator pedal when the accelerator lever has not been controlled but for controlling the valves so as to restrict the flow passage of the line in accordance with the instruction value of the accelerator pedal when the accelerator lever has been controlled.