A drive train (1) includes an internal combustion engine (2) and working hydraulics (4) having at least one hydraulic pump (7). When operated as a pump, the hydraulic pump (7) sucks hydraulic fluid from a tank (9) and delivers into a delivery line (10) that leads to the working hydraulics (4). When operated as a motor, the hydraulic pump (7) is supplied with hydraulic fluid from a hydraulic accumulator (25). The drive train (1) has a charge pump (20) to supply a charging circuit (23). The charge pump (20), when operated as a pump, sucks hydraulic fluid out of the tank (9) and delivers into a charge pressure line (22) that leads to a charging circuit (23), and the charge pump (20) when operated as a motor is supplied with hydraulic fluid from the hydraulic accumulator (25).

A hydrostatic drive includes a diesel engine and a hydrostatic adjustable machine which supplies multiple consumers in normal operation as a pump. The machine has a pressure/flow regulator to which is communicated, according to the load-sensing principle, the highest load pressure of the consumers, in particular when the machine is operated as a pump. In order to realize a start/stop function of the diesel engine, a previously charged high-pressure reservoir supplies the hydrostatic machine, which then acts as a starter motor for the diesel engine. In order to switch from pump to starter motor, the hydro-machine is adjusted over zero. In order for this switch to take place quickly and reliably, the pressure/flow regulator is deactivated by means of a switching valve and the adjustment device is supplied with an adjustment pressure medium via the switching valve, which medium is taken from the high-pressure reservoir or from an auxiliary reservoir.

A load sensing valve maintains a differential pressure at a set pressure by controlling a regulator in accordance with a differential pressure between a discharge pressure of a hydraulic pump and a load pressure of hydraulic actuators. A set pressure control device controls the set pressure. A controller controls the set pressure control device to reduce the set pressure more than when the work implement is being operated, when a predetermined determination condition that includes the work implement not being operated is satisfied.

A controller calculates the ratio between the sum of estimated demanded powers of a plurality of first actuators and the sum of estimated demanded powers of a plurality of second actuators, and calculates, on the basis of the ratio, first and second command values for adjusting allocation between a first allowable torque of a first pump and a second allowable torque of a second pump, and first and second regulators adjust the first and second allowable torques, on the basis of first and second output pressures of first and second torque control valves, such that the first and second allowable torques become values to which a predetermined allowable torque is allocated according to the ratio described above, and control the delivery flow rates of the first and second pumps such that the respective consumed torques of the first and second pumps do not become larger than the first and second allowable torques. Thus, the present invention efficiently performs torque allocation between the first and second pumps (a plurality of hydraulic pumps) to thereby enable effective utilization of the torque generated by the prime mover without wasting the torque.

A mixer drum driving apparatus includes an auxiliary fluid pressure pump that is provided independently of a fluid pressure pump and is capable of supplying a working fluid to a fluid pressure motor so as to cause a mixer drum to perform agitation rotation, a plurality of motors configured to drive the auxiliary fluid pressure pump to rotate, and a control unit that controls rotation of the mixer drum. When an engine is stopped during the agitation rotation of the mixer drum, the control unit drives the auxiliary fluid pressure pump to rotate by operating the plurality of motors selectively in accordance with a load of the mixer drum.

A prime mover and a plurality of hydraulic actuators, a hydraulic machine having a rotatable shaft in driven engagement with the prime mover and comprising a plurality of working chambers, a hydraulic circuit extending between a group of one or more working chambers of the hydraulic machine and one or more of the hydraulic actuators, each working chamber of the hydraulic machine comprising a low-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a low-pressure manifold and a high-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a high-pressure manifold. The hydraulic machine being configured to actively control at least the low-pressure valves of the group of one or more working chambers to select the net displacement of hydraulic fluid by each working chamber on each cycle of working chamber volume, and thereby the net displacement of hydraulic fluid by the group of one or more working chambers, responsive to a demand signal, wherein the apparatus further comprises a controller configured to calculate the demand signal in response to a measured property of the hydraulic circuit or one or more actuators.

A shovel includes a lower traveling body, an upper turning body turnably mounted on the lower traveling body, an engine provided in the upper turning body, a hydraulic pump and a hydraulic oil tank provided in the upper turning body, a plurality of hydraulic actuators driven by the hydraulic pump, and a hydraulic circuit connected to the hydraulic pump, wherein the hydraulic circuit includes a plurality of control valves configured to control flows of hydraulic oil between the hydraulic pump and the plurality of hydraulic actuators, and a unified bleed-off valve configured to collectively control bleed-off flowrates of the plurality of control valves, wherein the hydraulic circuit is configured so that a discharge pressure of the hydraulic pump becomes equal to or less than a predetermined pressure during start-up of the engine.

A method is provided for compensating for the flow rate of a variable capacity-type hydraulic pump such that, when a manipulation lever is manipulated, a discontinuous section, which has no change in the discharge flow rate of the hydraulic pump, is eliminated.

A hydraulic system is adapted to provide at least one of a fluid flow at a variable fluid pressure or a fluid flow at a variable fluid displacement. A pressure sensor measures a fluid pressure. A controller is in communication with the engine and the pressure sensor. Wherein, the controller sends an engine speed signal to operate the engine in an open state and controls the fluid displacement or the fluid pressure of the hydraulic system to a first load condition. Further wherein, the controller detects an engine speed and a fluid pressure of the hydraulic system with the pressure sensor when the engine is in the open state and the hydraulic system is in the first load condition. Further wherein, the controller operably calculates a total engine torque as a function of the detected engine speed and fluid pressure when the hydraulic system is in the first load condition.

A cargo vehicle includes a hydraulic pump driven by an engine, a cargo handling apparatus operated by hydraulic oil from the hydraulic pump, a cargo operating unit for performing an instruction operation to operate the cargo handling apparatus, an electromagnetic proportional control valve disposed between the hydraulic pump and the cargo handling apparatus, a valve controller that controls the electromagnetic proportional control valve depending on an operation state of the cargo operating unit, and a revolution detector that detects a revolution of the engine, wherein the valve controller controls the electromagnetic proportional control valve such that an opening degree of the electromagnetic proportional control valve is limited for a certain time when the revolution of the engine detected by the revolution detector is lower than a predetermined value.