Abstract: A hydraulic system for use in a work vehicle with a powered implement is disclosed. In one embodiment, the hydraulic system may include a first hydraulic circuit including a first hydraulic pump with a low pressure and low flow output, switch and valve; a second hydraulic circuit including a second hydraulic pump with a high flow and high pressure output, switch and valve; and a third hydraulic circuit including a third hydraulic pump with a high flow and high pressure output, switch and valve. The first, second, and third circuits each include an output selectively combinable with each other by an operator control which controls the switch and valve configurations. The hydraulic system has several configurations.

Abstract: With a hydraulic traveling vehicle, a controller is configured and arranged to switch a merging/diverging valve to a merging state when a working equipment is driven with the merging/diverging valve being in a diverging state and with turning of the hydraulic traveling vehicle being carried out, and when a required flow rate parameter for pressurized oil of the working equipment is greater than or equal to a prescribed threshold value, and to maintain the merging/diverging valve in the diverging state when the required flow rate parameter is less than the prescribed threshold value.

Abstract: The hydraulic drive system comprises an engine 1, a pump unit 100, a plurality of actuators 5a, 5b and 5c, a control valve unit 4, and engine revolution speed detecting means 4f. The pump unit 100 includes a pump tilting control mechanism 8 for load sensing control, and the control valve unit 4 includes a plurality of flow control valves 15a, 15b and 15c and pressure compensation valves 10a, 10b and 10c. The engine revolution speed detecting means 4f includes a first differential pressure reducing valve 14 for outputting, as an absolute value, a pressure depending on an engine revolution speed. The output pressure of the first differential pressure reducing valve 14 is introduced, as a target load-sensing differential pressure, to the pump tilting mechanism 8 via a line 127.

Abstract: A hydraulic circuit for heavy equipment having a variable control device is provided, in which variable relief valves for variably controlling operating pressure and flow rate of an option attachment are installed inside a main control valve, and pressure of the variable relief valves is variably controlled through selection of a preset option working mode.

Abstract: A fixed/variable hybrid system has modified constant flow open center hydraulic valves (“fixed/variable valves”), including an open center core, spools, a power core, and a tank galley. A small fixed displacement pump provides fluid at a constant rate to the open center core. A variable displacement piston pump provides fluid directly to the power core as needed. Activation of spools partially restricts the open center core causing an increase in fluid pressure that is communicated to the variable displacement piston pump's load sense signal port, causing the pump to increase fluid flow and pressure to the power core. Activated spools direct pressurized fluid from the power core to the applications through selected hydraulic ports. Activated spools also direct fluid flow from selected hydraulic ports via the tank galley to a hydraulic tank. Pumping the majority of fluid only on an as-needed basis results in significant efficiencies.

Abstract: The invention relates to a hydraulic control arrangement for actuating at least two consumers (2, 4) which can be supplied with pressure medium by means of a pump (6) with an adjustable delivery rate. Provided in the pressure medium flow path between the pump (6) and at least one of the consumers (2, 4) is an input pressure balance (60), by means of which a connection to a tank can be opened in a controlled manner. A power beyond connection (72) for connecting a power beyond consumer (74) branches off from a pressure medium flow path between the pump (6) and the input pressure balance (60). The adjustment of the input pressure balance takes place as a function of one of the load pressures of the consumer or of a power beyond consumer. Said hydraulic control arrangement permits a prioritized supply to the power beyond consumer and an increase in the regulating pressure difference when supplying power beyond consumers.

Abstract: A motor having two series of distribution ducts each having two groups of ducts. The displacement selector is able to occupy a large displacement position in which the first groups of distribution ducts of the first series are connected to a main duct while the second groups are connected to the other main duct, and a small displacement configuration in which the first group of distribution ducts of the first series is connected to a main duct, the second group of distribution ducts of the first series is connected to the other main duct and a bypass connection exists between the first and the second group of distribution ducts of the second series. The device has a restriction in order, in the small displacement configuration, to restrict this bypass connection.

Abstract: A rotation prioritizing valve serving as a flow rate control valve of a hydraulic pilot type is provided on the meter-in side of an arm cylinder. At the time of a combined operation of arm pulling and rotation, the rotation prioritizing valve is activated by rotation pilot pressure so that a meter-in flow rate of the arm cylinder is throttled to prioritize rotation movement. On the premise of the above, a switching valve is provided in a pilot line of the rotation prioritizing valve and switched so as to release a throttling effect of the rotation prioritizing valve when boom lowering movement is added to the combined operation of arm pulling and rotation so that a rotation prioritizing function is cancelled.

Abstract: When different implements are attached to an agricultural tractor, various hydraulic actuators on the implement are operated by connection to the hydraulic system on the tractor. A single hydraulic fluid connector on the tractor has first and second ports with a separate valve assembly provided to control fluid of fluid to and from each port. This enables one doubling-acting hydraulic actuator to be connected to both connector ports so that the fluid flow to and from the actuator is controlled. For a different implement, one single-acting hydraulic actuator can be connected to one connector port and another single-acting hydraulic actuator can be connected to the other port of the same connector. Individual operation of the valve assembly for each port in this case allows independent control of the two single-acting hydraulic actuators.

Abstract: An anti-saturation valve assembly (51) for use in a hydraulic system having priority (17) and auxiliary (25) load circuits, the priority circuit providing a priority load signal (19). The anti-saturation valve assembly includes a pressure sensor portion (61) which senses a decrease between pump pressure (23) and the priority load signal (19), and generates a force on a pressure reducing portion (63) to reduce, correspondingly, a pilot pressure (59): The reduced pilot pressure to a pilot valve (35) results in reduced flow to a pilot-operated main control valve (27) in the auxiliary load circuit (25), thus providing anti-saturation protection for the circuit, without throttling a main flow path and wasting substantial hydraulic power.

Abstract: A hydraulic system for actuating a clutch and/or a variable speed drive unit of a belt-driven conical-pulley transmission of a vehicle, such as a commercial vehicle, and having a variable transmission ratio and a torque sensor. The hydraulic system includes at least one hydraulic energy source. A selector and check valve is provided for supplying additional components besides the torque sensor and is connected between the hydraulic energy source, the additional components, and the torque sensor in such a way that the torque sensor includes priority in being supplied with hydraulic medium.

Abstract: The invention discloses a hydraulic control arrangement for controlling a number of consumers, particularly of a mobile working machine. In addition to the consumers of the control arrangement, an additional consumer should be able to be connected to a power beyond port. All consumers and power beyond consumers are supplied with hydraulic fluid by a pump. An input pressure scale is provided downstream of the pump, and the greater of the load pressures of the consumers or of the at least one power beyond consumer is applied to the control port of said input pressure scale.

Abstract: There is provided a control system for electro-mechanical transmission that is selectively operative in a plurality of fixed gear modes and continuously variable modes comprising first and second electrical machines and four hydraulically-actuated clutches in fluid communication with a hydraulic circuit comprising first, second and third pressure control devices and first and second flow management valves. The control system is operative to selectively actuate the pressure control devices and the flow management valves based upon a demand for torque, presence of a fault, and temperatures of the electric machines.

Abstract: A change-speed control system is provided for a utility vehicle having a stepless change-speed apparatus for speed-changing an engine output and transmitting the speed-changed output to a traveling unit. The system includes an engine speed governor for adjusting speed of the engine, an accelerator controller and a change-speed control linkage device for providing operative displacements in the stepless change-speed apparatus and the engine speed governor in association with an operation of the accelerator controller. The change-speed control linkage device sets an operation amount for the stepless change-speed apparatus and an operation amount for the engine speed governor in correlation with the operation amount of the accelerator controller, such that an acceleration ratio for the engine speed is greater than an acceleration ratio for the stepless change-speed apparatus until the engine reaches a predetermined speed and also the stepless change-speed apparatus reaches a predetermined speed.

Abstract: An apparatus for easing an impact on a boom of an excavator and a method of controlling the same are disclosed, which can minimize the vibration occurring in the boom due to the impact on a boom cylinder by actively controlling an amount of hydraulic fluid being supplied to the boom cylinder when the operation of the boom cylinder is suddenly stopped due to an operator's sudden manipulation of an operation lever for a working device.

Abstract: A slide of a press machine is driven by composite thrust of thrust of an electric (servo) motor SM (via a screw/nut mechanism from the electric motor) and thrust of hydraulic cylinders SYL1, SYL2 to which pressure oil is supplied from a constant, high pressure source. A slide control device controls the electric motor SM and the hydraulic cylinders SYL1, SYL2, based on a slide position signal and a motor angular velocity signal, and at the same time, makes the hydraulic cylinder SYL1 work as a pump during a period when slide load is small, charging pressure oil to the constant, high pressure source by using the thrust transferred from the electric motor to the hydraulic cylinder SYL1 through the screw/nut mechanism and the slide.

Abstract: Temperature of each cooling target fluid is detected. When the flow rate of a cooling target fluid passing through a cooling system is high, the fan revolution speed of a cooling fan of the cooling system is controlled to achieve a target fan revolution speed so that the detected temperature of the cooling target fluid reaches a preset target temperature. In cases where the engine is in a low idling state, the flow rate of each cooling target fluid passing through the cooling system is reduced. The fan revolution speed of the cooling fan is controlled to achieve a new target fan revolution speed that is lower than the target fan revolution speed.

Abstract: An electro-hydraulic system for operating a cooling fan and providing hydraulic fluid to a power steering system of the vehicle includes a hydraulic pump unit including first and second fixed displacement pumps and a common drive shaft for these pumps. A hydraulic fluid reservoir is connected to the inlet of each of the pumps. A priority valve is operatively connected to the outlet of the first pump and has an outlet connectible to the power steering system. This valve also has a second outlet connectible to a hydraulic motor for the cooling fan. This valve is arranged to provide a constant flow of hydraulic fluid to the power steering system. A hydraulic line connects an outlet of the second pump to the hydraulic motor. Hydraulic fluid flow through this line is combined with hydraulic fluid flow from the first pump to drive the motor.

Abstract: A hybrid actuation system comprises first and second actuator arrangements (10, 12) arranged to apply first and second output loads respectively to a common element (14). A control method for controlling the operation of the hybrid actuation system includes the steps of supplying first and second demand signals to the first and second actuator arrangements (10, 12) respectively to cause movement of the common element (14) into a demanded position, monitoring the first and second output loads applied by the first and second actuator arrangements (10, 12) and generating an output signal indicative of the difference between the first and second output loads. The first and second demand signals are corrected in response to the output signal to compensate for any difference between the first and second output loads, thereby to ensure the first and second output loads applied to the common element (14) are substantially identical and synchronized.

Abstract: An earthmoving vehicle has an operating arm that is raised and lowered by a hydraulic system. The hydraulic system includes a drain line and at least one actuator connected to the operating arm. The actuator defines a variable-volume chamber connectable to the drain line to lower the operating arm. The hydraulic fluid discharged from the chamber flows through a proportional safety valve adjacent to the actuator and a distributor valve that is driven by a pilot control valve to allow free flow to the drain line. Thus, the lowering of the operating arm is controlled solely by the proportional safety valve.

Abstract: Maximum charging power of a battery (63) is set by a battery-charging power setting unit (75), while maximum discharging power of the battery (63) is set by a battery-discharging power setting unit (76). Lower and upper limit of generator output power is set by a generator output power setting unit (77). A generator/battery power distribution determining unit (81) distributes power between the battery (63) and the generator (62) using the set values above.

Abstract: A control device for a working machine according to the present invention comprises a capacity variable pump for supplying working oil, a controller for controlling the discharge amount of the pump, a control valve for controlling the working oil discharged from the pump, a hydraulic actuator operated by the working oil from the control valve, an operating lever for operating the hydraulic actuator, and a relief valve to be operated when the pressure of the working oil is a relief pressure or more. The controller has a dynamic emulation model of a hydraulic driving device, and is constituted to estimate the pressure oil flow rate passing through the relief valve from the emulation model according to the operation amount of the operating lever, and to control the pump flow rate of the pump so that the relief flow rate estimation value gets close to zero. According to this, relief loss can be precisely reduced without generating a response delay or pressure loss, and the power can be saved.

Abstract: A failure detection device for a hydraulic motor according to the present comprises a hydraulic pump (3) that is driven by a prime mover (2); a hydraulic motor (1) that is driven by hydraulic oil discharged from the hydraulic pump (3); an abnormality detection device (35) that detects a sign of abnormal operation of the hydraulic motor (1); and a warning device (39, 40) that issues a warning when the sign of the abnormal operation of the hydraulic motor (1) is detected by the abnormality detection device (35).

Abstract: First and second hydraulic pumps each adapted to operate plural actuators are activated by separate electric motors respectively. In accordance with signals provided from a controller on the basis of operations of levers, the number of revolutions of the electric motor and that of the electric motor are controlled each independently and simultaneously to control the discharge rates of both hydraulic pumps.

Abstract: The present invention is directed to supply a desired amount of working oil needed by an option apparatus in the case that a combined work is performed by engaging an option apparatus to a work apparatus.

Abstract: Hybrid powered construction equipment is capable of making effective use of the output energy of an engine; increasing operating speed while keeping noise level low, and assuring operation power more than the performance of the engine. To this end, the hybrid powered construction equipment has a hydraulic pump powered by the engine; hydraulic actuators activated by discharge oil from the hydraulic pump; a motor-generator working in conjunction with the engine; and a battery for storing electric power generated by the electric motor-generator, the construction equipment further comprising a power-up switch disposed in an operating lever or operation panel and a controller which inputs a signal released from the power-up switch, wherein the controller constantly controls the revolution speed of the engine in response to a signal from the power-up switch and controls the output torque of the electric motor-generator such that torque for assisting powering of the hydraulic pump is output.

Abstract: A hydraulic circuit comprises a first and a second merging line capable of supplying pressure oil from a third pump for a third circuit to directional control valves in a first and a second circuit, respectively, and a merging valve for selectively communicating or cutting off the first and the second merging line with or from the third pump. The merging valve has a first shift position at which the third pump is connected to the second merging line, and a second shift position at which the third pump is connected to the first and the second merging line. The merging valve is shifted continuously between the shift positions. The hydraulic circuit can efficiently distribute pressure oil supplied from the third pump to the first and/or second circuit as well, and can prevent lowering of the operability of each of actuators connected to the first or second circuit.

Abstract: A fluid system includes first and second control valves that control fluid communication with first and second actuators. The first control valve may combine fluid flow from a second end port of the first actuator with fluid flow from a pressurized fluid source when providing a supply of fluid to a first end port of the first actuator. The first and second control valves include first and second signal ports in fluid communication with the supply of fluid to the first and second actuators. A resolver outputs a resolved signal pressure equal to the greater of a first signal pressure output by the first signal port and a second signal pressure output by the second signal port. A compensator in fluid communication with the first control valve and the first actuator controls fluid flow from the first control valve to the first actuator based on the resolved signal pressure.

Abstract: To generate a magnetic resonance angiograph, a patient is injected with a contrast-enhancing agent (210). An ellipsoidal central portion of k-space (300) and a first surrounding region (310) are continuously sampled (220). A portion of each central data set (300, 310) is reconstructed (230) into a low-resolution volume and maximum-intensity-projected (240) onto a line. The maximum intensity projection (240) is processed (250) in order to detect the arrival of the contrast enhancing bolus within a volume of interest. Upon detection of the arrival of the bolus, the acquisition of a high-resolution magnetic resonance angiograph is triggered (260) in which higher phase encode portions (310, 420) of k-space are sampled. The central data set (300) along with the higher phase encode views (310, 420) are reconstructed (290) into a high-resolution magnetic resonance angiogram.

Abstract: Method of sharing hydraulic fluid, includes: inputting first signal from a first manual control and second signal from a second manual control; sending a first control signal controlling a first valve in response to first signal; sending a second control signal controlling a second valve in response to second signal, wherein the first valve and second valve direct flow through a first sub-circuit and a second sub-circuit, respectively, wherein the first sub-circuit moves a boom arm and the second sub-circuit moves an implement; determining whether the boom arm and implement are in a first, second, third, or fourth condition; modifying at least one of the first and second control signals when the boom arm and implement are in first or second conditions; and controlling the first valve using the unmodified or modified first control signal and controlling the second valve using unmodified or modified second control signal.

Abstract: A method of determining shift points in a step gear transmission system to maximize fuel economy is disclosed. In operation, the method uses fuel economy data from a first gear ratio to determine a first series of constant fuel consumption curves for the first gear ratio. The method then uses fuel economy data from a second gear ratio to determine a second series of constant fuel consumption curves for the second gear ratio. Next, the method determines points of intersection where a respective fuel consumption curve for the first gear ratio intersects its corresponding fuel consumption curve for the second gear ratio. A decision curve is generated from the points of intersection.

Abstract: A multiple valve apparatus is formed of a priority valve mechanism for dividing an operating liquid into a priority flow and a surplus flow, at least one switching valve mechanism attached to the priority valve mechanism, a parallel line for guiding the surplus flow discharged from the priority valve mechanism to an input port of the at least one switching valve mechanism, a tank line for discharging the operating liquid to a tank, and an urgent valve situated between the parallel line and the tank line. The urgent valve is operated in a predetermined condition to regulate an operation actuated by the surplus flow through the at least one switching valve mechanism. Therefore, the supply of the operating fluid only to the switching mechanism can be stopped or regulated by this simple structure, and an automatic stop or regulating function of an actuator can be achieved in the apparatus.

Abstract: The invention provides a hydraulic circuit for construction machines, capable of obtaining a satisfactory suspending capability during load suspending work, and having an improved operation efficiency with a decrease in the working speed of a load suspending operation minimized, the hydraulic circuit including a suspension mode switch for setting a working mode to a suspension mode, a lift detecting sensor for detecting a predetermined actuator which has been operated to a load lifting side, a relief valve control unit capable of freely setting an object pressure of the relief valve 14 to a normal set level and a high set level higher than the normal set level, a cutoff valve control unit capable of freely switching the cutoff valve to a cutoff operation executing mode and a cutoff operation disengaging mode, and a controller adapted to increase a set pressure of the relief valve by outputting an instruction to the relief valve control unit when the controller receives a suspension mode signal and a lift dete

Abstract: The present invention is directed to a computer based control system for controlling hydraulic and electromechanical actuators on a power machine, such as a skid steer loader. The computer based control system is configured to implement a number of features to enhance certain operational aspects of the power machine. One such feature includes an operator actuable selector which provides a selector signal based on an operator input. A controller receives the selector signal and provides an auxiliary output signal to control an auxiliary valve in a selected one of an on/off mode and a proportional mode based on the selector signal.

Abstract: It is intended to keep low the moment of inertia of a boom, etc. and maintain the whole of a working machine in good weight balance. At the same time, a highly efficient recovery of energy is to be attained to increase a continuous working time of a battery. A battery-powered working machine using a battery as a power source is provided. Rotation of a rotatable superstructure 12 and rising and falling motions of a boom 28 are performed directly by electric motors 22 and 34. The recovery of energy is attained by utilizing the electric motors 22 and 34. An arm 30 and a bucket 32 both located remote from a centroid position of the machine are actuated by an arm cylinder 38 and a bucket cylinder 40, which are hydraulic actuators less heavy than electric motors. Further, a hydraulic pump 18 for supplying those hydraulic actuators with a hydraulic oil is actuated by a hydraulic pump actuating electric motor 20 which utilizes the battery 14 as a power source.

Abstract: A bi-directional power conversion system interconnects hydraulic and electrical power systems on-board a vehicle such as an air-craft, whereby the power conversion system can selectively convert available electrical power to needed hydraulic power or vice versa. The power conversion system includes a hydraulic machine (15) connected to the hydraulic system (10) of the vehicle, an electrical machine (20) connected to the electrical system (3) of the vehicle through a power converter and control unit (22), a rotational drive shaft (14) mechanically interconnecting the hydraulic machine (15) and the electrical machine (20), and a priority and safety control unit (26) that controls the operation of the system.

Abstract: The present invention provides a novel power generating device, wherein the rotary inertial force of a fly wheel cooperating with a pneumatic auxiliary power apparatus is employed to maintain that the fly wheel rotates continuously and acceleratingly and outputs power. The part of the output force of the fly wheel is used to drive an air compressor for generating compressed air, to be input into a pneumatic motor of the pneumatic auxiliary power means so that the output power of the pneumatic motor is fed back to the fly wheel in order that the fly wheel maintains the inertial force to rotate continuously. The fly wheel also drives a cam type control apparatus so to control the compressed air that it supplies intermittently to the pneumatic motor for driving the fly wheel. Additionally, the fly wheel is preferably mounted with a weight, and a compensation device for beating the fly wheel in order to increase inertial torque each time when the weight rotates to a predetermined angle.

Abstract: The maintenance device consists of a hydraulic insulation unit (2) mounted between the supply circuits of a cylinder (1). The insulation unit (2) comprises a sluice (9) which has, at each of its two openings, an anti-return valve, one of which, the primary valve (11) is hydraulically connected to the outlet chamber (6) of the shaft (7) of the cylinder (1) and opens toward said chamber; and a safety valve (13) opening in the same direction, with the latter valve closing at a different rate than the primary valve closes. The invention is useful for maintaining the shaft of any cylinder in position, particularly a charged cylinder, and it is of interest to manufacturers of hydraulic devices, particularly lifting cylinders, as well as those who use them.

Abstract: The battery-driven hydraulic excavator comprises an electric motor driven by power from the battery, a hydraulic pump driven by the electric motor, and a plurality of hydraulic actuators driven by operating oil from the hydraulic pump. There are provided supply lines for feeding the operating oil in an oil tank from the hydraulic pump into the hydraulic actuators. A differential pressure gauge for detecting the flow rate of operating oil is provided in a main supply line for joining operating oil which were not fed into the hydraulic actuators to return it to the oil tank. Control is made so that power in inverse proportion to the flow rate detected by the differential pressure gauge is supplied to the electric motor. Thereby, the life of the battery can be extended.

Abstract: A multiple hydraulic distributor device, having an antisaturation function wherein flow of hydraulic fluid is divided independently of load, which includes a hydraulic distributor device having a number of distributor devices assigned to controlling respective loads, which are stacked up face to face against each other as a stack and individually arranged in such a way that the stack has a common line passing through the stack for supplying working fluid under pressure originating from a source including a pump associated with a flow/pressure control device, a common return line for returning working fluid to a tank, and a common transmission line for transmitting control fluid at a pressure of highest load towards the control device for controlling the pump; a shut-off device arranged in the transmission line between a first group of distributors for which the transmission line is connected to the flow/pressure control device for controlling the source, and at least a second group of distributors for which t

Abstract: A hydraulic motor is configured to drive a cable spool. A first fluid diverting valve is hydraulically connected between a discharge of a vehicle steering pump and the hydraulic motor. The first fluid diverting valve is configured to divert full fluid flow to a vehicle power steering box, and to divert full fluid flow to the hydraulic motor. A second fluid diverting valve is hydraulically connected between the first fluid diverting valve and an inlet of the vehicle steering pump. The second fluid diverting valve is configured to divert full fluid flow from the first fluid diverting valve to the hydraulic motor and to divert full fluid flow from the first fluid diverting valve to the inlet of the vehicle steering pump, bypassing the hydraulic motor and permitting fluid flow between the inlet of the hydraulic motor and the outlet of the hydraulic motor through the second fluid diverting valve so that manual operation of the winch is permitted.

Abstract: First and second boosters 1, 2 which, through reciprocating motions of oil hydraulic cylinders 6a, 6b, pressurize water sucked into plunger chambers 3a, 3b to a superhigh pressure level are connected in parallel to a water discharge line 8, First and second three-position directional control valves 9, 10 are arranged between the oil hydraulic cylinder of each booster and a hydraulic pump 11, 12 so as to cause the hydraulic cylinder to perform a reciprocal movement. The first and second boosters 1, 2 are provided respectively with first and second sets of forward stroke and return stroke sensors (29, 29'; 30, 30') for detecting positions adjacent to respective ends of pressing and suction strokes.

Abstract: A hydromechanical transmission shifting control system and method includes a hydromechanical transmission and a number of clutches connected to the transmission. A microcontroller receives various signals generated by the operator, engine, transmission, and the load. The microcontroller controls the ratio of the input to output speed of the transmission as well as the engagement or disengagement of the number of clutches based upon the various input signals.

Abstract: A vehicular brake booster using fluid pressurized by a hydraulic power steering system hydraulic pump. Fluid pressure is controlled by using a pressure regulator in the pump output and by electronically switching fixed orifices in a boost developing valve controlling fluid flow within the power steering system. Additional control is effected by electronically opening and closing apply and relief valves controlling fluid flow respectively to and from a brake power booster for differing periods.

Abstract: A hydraulic drive system comprises a controller (12) and several condition sensors. A boom-up target flow rate setting section determines a boom-up target flow rate based on signals from a pressure sensor (11) and a rotational speed meter (16), a pump delivery rate detecting section determines a pump delivery rate based on signals from a tilt angle sensor (15) and the rotational speed meter (16), a differential pressure detecting section and a center bypass flow rate calculating section determine a center bypass flow rate based on signals from pressure sensors (9, 10), a boom cylinder calculating section determines a boom cylinder flow rate from the pump delivery rate and the center bypass flow rate, and a first pump target displacement volume calculating section calculates a first pump target tilt angle .theta..sub.1 in accordance with the difference between the boom-up target flow rate and the boom cylinder flow rate. In this case, .theta..sub.1 is larger than a second pump target tilt angle .theta..sub.

Abstract: A control system and method for a plurality of motors utilize one, and only one, motor drive unit that provides power to drive any one of the motors. The system and method also utilize a controller that controls which of the motors to energize. Power from the motor drive unit can be communicated to one of the motors selected by the controller, or power from a primary power source can be communicated to one or more of the motors selected by the controller. Sequencing of the motors to and from the motor drive unit and the primary power source, and between the two, is automatically controlled, such as based on how long each of the motors has been used. Accordingly, a method of controlling a plurality of motors comprises: defining a motor utilization criterion; sensing a parameter affected by the number of the motors that are operating; and sequentially starting and cumulatively operating ones of the motors selected in response to the motor utilization criterion and the sensed parameter.

Abstract: In a hydraulic system, several consumers (4) are supplied by a common pump. In so doing, the consumers (4) are controlled by control valves (6). When the required oil flows exceed the quantity which can maximally be delivered, a control becomes operative which allows to adapt the reference value signals by which the valves (6) are controlled, to the actually measured pump flow, preferably to the weighting of the actually measured pump flow with the maximally predetermined pump flow.

Abstract: In a hydraulic drive system for a construction machine, first flow control mechanism includes first and second flow control valves (11a, 11b) and first interlock mechanism (54, 55) for interlocking the first and second flow control valves with first directional control mechanism (7), and second flow control mechanism includes third and fourth flow control valves (12a, 12b) and second interlock mechanism (56, 57) for interlocking the third and fourth flow control valves with second directional control mechanism (9). First pressure control mechanism includes at least first pressure control valve (13a) operated in response to a pressure signal in a valve-closing direction, and second pressure control mechanism includes only second pressure control valve (15b) operated in response to the pressure signal in a valve-closing direction.

Abstract: Hydraulic actuators are fed by a single flow-rate generator, each being connected to it through a proportional directional valve, the unit including at least one auxiliary valve fed by the flow-rate generator and producing a pressure which is normally equal to a regulation pressure increased by a constant, and in each proportional directional valve an actuating device causes the compensating spool to respond to the pressure produced by the auxiliary valve.

Abstract: In a hydraulic circuit a positive-displacement pump has a flywheel. An actuation motor is attached to the positive displacement pump. The pump is capable of directing liquid flow either towards the tank or towards a hydraulic cylinder. The control of flow direction is determined by a first valve which is connected on the output side of the pump in order to discharge the flow of the positive displacement pump either to the tank or to the cylinder. The opening speed of the first valve is controlled. A bistable valve feeds the pilot line of the first valve. A distribution valve, connected with the output side of the pump feeds two pressure lines.