Abstract: A construction machine includes: a work arm rotatably mounted at a construction machine main body; a work tool mounted at the work arm; an attitude decision device that decides an attitude of the work arm or the work tool relative to the construction machine main body; a follow-up enabling device that allows the work arm or the work tool to follow a displacement of a contacting object that comes into contact with the work tool and applies an external force to the work tool, by adjusting the attitude of the work arm or the work tool decided by the attitude decision device; and a switching device that selects whether or not to allow the work arm or the work tool to follow the displacement of the contacting object via the follow-up enabling device.

Abstract: A method of controlling a work vehicle includes detecting an operational condition of a powertrain which is adapted to propel the vehicle, wherein a power source in the powertrain is adapted to operatively drive at least one variable displacement pump, wherein the pump is adapted to operatively drive at least one hydraulic actuator via hydraulic fluid for moving a work implement and/or steering the vehicle. The method further includes comparing the detected operational condition with a predetermined critical condition, limiting a maximum available displacement of the pump and thereby establishing an available pump displacement range if the magnitude of the detected operational condition is within the predetermined critical condition, detecting a hydraulic load associated to the actuator, and adjusting the pump displacement of the pump in response to the detected hydraulic load within the available pump displacement range.

Abstract: The present invention is intended to provide a technology that can utilize the advantages of both a load sensing control and a regeneration circuit without causing any problem. A regeneration circuit is added to a hydraulic circuit provided with a hydraulic pressure signal line for detecting a hydraulic pressure value of a circuit and controlling a volume of hydraulic fluid to a cylinder 1 with reference to the detected value. A pressure reducing valve 6 that outputs a reduced pressure as an operating signal to a pump 2, and subsequently the controlling means 5 causes the pressure reducing valve 6 to output a pressure reduction command to a pump 2 and thus to reduce a discharge rate from the pump 2, when the regeneration circuit is in a regeneration state.

Abstract: A hydrostatic transmission having a hydraulic pump that is fluidly connected to a hydraulic motor. The transmission also has a pressure control valve that has first and second stages and is fluidly connected to the hydraulic pump. By utilizing the pressure control valve when the first stage of the pressure control is at a minimum pressure the second stage determines the minimum charge pressure setting for the hydrostatic transmission.

Abstract: A current load rate of an engine 10 is computed and a maximum absorption torque of at least one hydraulic pump 1, 2 is controlled so that the load rate is held at a target value. Engine stalling can be prevented by decreasing the maximum absorption torque of the hydraulic pump under a high-load condition. When an engine output lowers due to environmental changes, the use of poor fuel or other reasons, the maximum absorption torque of the hydraulic pump can be decreased without a lowering of the engine revolution speed. Further, the present invention is adaptable for any kinds of factors causing a lowering of the engine output, such as those factors that cannot be predicted in advance or are difficult to detect by sensors. In addition, because of no necessity of sensors, such as environment sensors, the manufacturing cost can be reduced.

Abstract: A hydraulic drive system for a construction machine allows automatic changes of the operational characteristics of a boom directional control valve by judging whether or not a hydraulic boom cylinder needs driving pressure at the time of a boom lowering operation. A solenoid switch valve is controlled such that a pilot oil passage with a pressure reducing valve is selected to set the limit of a boom-lowering spool stroke of a boom directional control valve to a middle position L1 when the rod-side pressure of a hydraulic boom cylinder detected by a pressure sensor is less than a threshold value and such that a pilot oil passage is selected to set the limit of the boom-lowering spool stroke of the boom directional control valve to a maximum stroke position L2 when the rod-side pressure is equal to or greater than the threshold value.

Abstract: A concrete agitating drum (1) is driven by a hydraulic motor (81). A connection switch-over valve (20) is arranged to have a function to regulate a flow cross-sectional area of pressurized working oil supplied to the hydraulic motor (81) from a variable capacity hydraulic pump (10). The variable capacity hydraulic pump (10) is driven by a combustion engine (60) together with a charge pump (11). When a discharge pressure of the charge pump (11) is low, the connection switch-over valve (20) maintains a small flow cross-sectional area to rotate the agitating drum (1) at a low rotation speed so that fuel consumption of the combustion engine (60) is suppressed to be small. When the discharge pressure of the charge pump (11) becomes high, the connection switch-over valve (20) enlarges the flow cross-sectional area, thereby realizing a rated rotation speed of the agitating drum (1).

Abstract: To permit a precise and easy adjustment of a pump absorption torque of a main pump in accordance with environmental conditions when a sub-pump different in characteristics from the main pump is connected to a prime mover. A main controller 12 includes a processor means for setting the level of an absorption torque of a cooling fan pump 20 at a maximum absorption torque in use, a processor means for incrementing an adjustment target absorption torque for a main pump 13 at a slow rate from a sufficiently small pump absorption torque, and a processor means for repeating loading of a load factor signal and the increment of the adjustment target absorption torque as long as “NO” is determined by a fourth determination means, and a processor means for storing the adjustment target absorption torque as an adjustment value when “YES” has been determined by the fourth determination means.

Abstract: A hydrostatic drive system (1) has a load-sensing pump (2) with an adjustable discharge volume and at least one consumer connected to the pump (2). The discharge volume of the pump (2) can be set by a discharge volume control device (6) that sets the delivery pressure of the pump available in a delivery line (4) of the pump (2) so that it is higher by a pilot control pressure difference than the load pressure of the consumer. The discharge volume control device (6) can be actuated by an electronic control device (7) functionally connected with a sensor device (9) for measuring the load pressure of the consumer and with a sensor device (8) for measuring the delivery pressure available in the delivery line (4). A circulation device (15) is associated with the delivery line (4) to control the connection of the delivery line (4) with a reservoir (3).

Abstract: On the basis of reference torque and torque correction amount output units (T1 and T2), a torque control command pressure is calculated so that the input torques of first and second pumps are increased. The calculated torque command instruction pressure is then supplied as external command pressure to the varying mechanism of a regulator used for the first and second pumps so as to prevent the input torques of the first and second pumps from being decreased more than necessary. As a result, even when three variable displacement hydraulic pumps are used with the discharge pressure of one of the hydraulic pumps reduced by a pressure reducing valve and further the input torques of the other two hydraulic pumps are decreased by that pressure, the engine output can be efficiently utilized, and the work rate does not decrease.

Abstract: The invention relates to a hydraulic circuit arrangement for setting the delivery volume of a pump, with an electrically activatable control-valve unit, by means of which, alternately, an active side of a servo system can be acted upon with pressure and, at the same time, its passive side can be relieved to the tank, and with a device for pressure limiting pressure regulation, which comprises pressure limiting valves, by means of which the working lines of the pump can be connected to the servo lines. To reduce the servo pressure load and improve the reaction time, check valves which shut off in the direction of the servo system are provided, by means of which the two servo sides can be connected in each case to the charge pressure via a relief line. Moreover, the device for Pressure limiting pressure regulation comprises an orifice which can be positioned in a line leading to the passive servo side. The invention relates, furthermore, to a method for pressure.

Abstract: A fluid pressure actuator includes an output cylinder, a fluid pressure pump, an electric motor, a first output cylinder passage, a second output cylinder passage, a return passage and a swash plate control cylinder. The output cylinder includes a first output cylinder chamber, a second output cylinder chamber and an output piston arranged between the first output cylinder chamber and the second output cylinder chamber. The fluid pressure pump includes a first supply and discharge port, a second supply and discharge port and a swash plate for changing displacement of the fluid pressure pump. The electric motor drives the fluid pressure pump. The first output cylinder passage connects the first output cylinder chamber and the first supply and discharge port. The second output cylinder passage connects the second output cylinder chamber and the second supply and discharge port.

Abstract: The invention relates to a hydraulic control system for providing at least one hydraulic consumer with a pressure medium. Said system comprises an LS pump system and a metering port for adjusting the pressure medium volume flow rate towards the consumer. The LS line is connected to a pressure medium sink via a current regulator. The invention is characterized in that the current regulator can be adjusted depending on the pump rate in order to modify the pressure drop at the metering port.

Abstract: An actuator control system is disclosed. The actuator control system may have a pump and at least one actuator. The actuator control system may further have an actuator valve configured to control the at least one actuator. The actuator control system may also have a pump pressure sensor configured to determine a pump pressure value and a load pressure sensor configure to determine a load pressure value. The actuator control system may additionally have a controller configured to receive the pump pressure value and the load pressure value. The controller may further be configured to compare the pump pressure value and the load pressure value, and selectively implement a primary control strategy and a secondary control strategy based on the comparison.

Abstract: It is an object, in a hydraulic stepless transmission, to change capacity of a hydraulic pump to thereby make output characteristic different between forward and reverse travel and obtain efficient output characteristics. In the hydraulic stepless transmission formed of the hydraulic pump 10 and a variable displacement-type hydraulic motor 11 and including control means 4, 10 for carrying out capacity control based on a load received by the hydraulic stepless transmission, a pressure control valve 204 is connected to control pressure portions of the control means 4, 10 for carrying out the capacity control according to pressure in a hydraulic circuit 13 on a discharge side of the hydraulic pump 10 to carry out the capacity control of the variable pump and the motor 11.

Abstract: A dual mode control system for a hydraulic circuit (200) having a variable displacement pump (216) includes at least two actuators, each controlled by a respective valve. The valves are connected in series with a pressure sensor (250) measuring a pressure of fluid between the first valve (224) and the second valve (234) and relaying a signal to the electronic controller (202). The electronic controller (202) operates in a first mode, varying the displacement of the pump (216) based on a command signal operating at least one of the valves, and operates in a standby mode, varying the displacement of the pump (216) based on the signal from the sensor, when both valves are in their respective neutral positions.

Abstract: A variable capacity hydraulic pump (10) drives a concrete agitating drum (1) via a hydraulic motor (81). A hydraulic actuator (14) regulates a discharge flow rate of the hydraulic pump (10) depending on an actuator driving pressure. A load sensing valve (40) generates the actuator driving pressure by reducing a discharge pressure of the hydraulic pump (10) according to a differential pressure between the discharge pressure and a load pressure acting on the hydraulic motor (81). A shut-off valve (20) shuts off supply of the pressurized oil discharged from the hydraulic pump (10) to the hydraulic motor (81). Due to this action, when the differential pressure increases beyond a predetermined differential pressure, an unload valve (30) drains the discharged oil, thereby preventing the hydraulic pump (10) from generating noise due to an excessive increase in the discharge pressure.

Abstract: A vehicle is disclosed having a hydraulic system. The hydraulic system includes a pressure regulator that maintains the output pressure from a hydraulic pump above a predetermined minimum pressure.

Abstract: A load sense valve assembly includes a first valve in flow communication with a pump discharge line, a second valve in flow communication with the first valve, and a third valve in flow communication with the first valve. The first valve can be a solenoid actuated directional control valve. The second and third valves can be hydraulic pilot actuated directional control valves.

Abstract: A vehicle with a load sensing hydraulic control system is disclosed.

Abstract: The disclosure relates to a feed pump for hydraulic media having an input and an output. A pressure-reducing element is connected to the output, at the output of the element the system pressure being present and the output being connected to a consumer, wherein the output is connected to the first input of a pump controller, the second input being connected to the output of the pressure-reducing element, and wherein the pump controller adjusts the feed pump toward maximum delivery if the system pressure is smaller than a minimum pressure or if the system pressure is smaller than the feed pressure, and wherein parallel to the pump controller a pressure limiter is switched such that at the first input thereof the feed pressure is present and at the control input the system pressure is present, wherein the pressure limiter opens if the feed pressure is greater than a desired value.

Abstract: A method of controlling a motor includes monitoring a pressure in a circuit supplying a pressurized fluid to the motor, determining a difference between the monitored circuit pressure and a desired circuit pressure, and determining an actuator command for an actuator that is capable of adjusting a pressure of the pressurized fluid supplied to the motor. The actuator command is determined based on the difference between the monitored circuit pressure and the desired circuit pressure, and is independent of a position of the actuator. The method also includes operating the actuator based on the actuator command.

Abstract: A hydraulic circuit 100 having a simple structure can recover energy of fluid. Hydraulic circuit 100 comprises a boom cylinder 22, a hydraulic pump 31, a motion switchover valve 32, a hydraulic pressure regulation system 37 and a recovery pipe 36. Hydraulic pump 31 is driven by a drive source 15 so as to deliver fluid to boom cylinder 22. Motion switchover valve 32 is disposed between boom cylinder 22 and hydraulic pump 31 so as to switch a motion of boom cylinder 22. Hydraulic pressure regulation system 37 adjusts a differential pressure of motion switchover valve 32 between a delivery port 31a of hydraulic pump 31 and a suction port of boom cylinder 22 to a predetermined value. Recovery pipe 36 supplies hydraulic pump 31 with fluid from motion switchover valve 32 to which the fluid is drained from a drain port of boom cylinder 22.

Abstract: A control for a variable displacement pump disposed in a hydraulic system obtains a requested signal from a manual control device and provides a command signal to a valve operating to adjust a displacement setting of the variable displacement pump. The control provides the command signal based on the requested signal, and scales the requested signal based on a sensed or calculated load of the system.

Abstract: A hydraulic circuit is disclosed. The hydraulic circuit may have a variable displacement pump. The variable displacement pump may have a fluidic displacement control configured to vary a flow of pressurized fluid based on a fluid signal and an electronic displacement control configured to vary the flow of pressurized fluid based on an electronic signal. The flow of pressurized fluid may be controlled by the one of the fluidic and electronic displacement controls that requests the smallest flow of pressurized fluid. The hydraulic circuit may also have a control valve connected between the pump and the fluidic displacement control, and the control valve may be configured to transmit the fluid signal to the fluidic displacement control.

Abstract: A hydraulic system includes a variable displacement hydraulic pump connectable to a power source, a hydraulic motor, a fluid circuit, a pump displacement control, and a controller. The pump has an inlet for receiving fluid, an outlet for discharging pressurized fluid, and a pump displacement input. The motor has an inlet for receiving pressurized fluid and an outlet for discharging spent fluid. The fluid circuit includes a supply conduit for conducting fluid discharged by the pump to the motor and a return conduit for returning fluid discharged by the motor to the pump. The pump displacement control cooperates with the pump displacement input to vary pump displacement. The controller communicates with the pump displacement control to control the pump output such that the motor is driven at a constant speed to thereby drive a generator connected to the motor at a constant speed despite speed fluctuations of the power source.

Abstract: With respect to a method of controlling a pump flow rate of a hydraulic pump, a method having a small flow rate command value is selected between a pressure feedback control for controlling the pump flow rate based on a set pressure (a cutoff pressure) and a pump pressure, and, an ordinary control for controlling the pump flow rate based on operation information, and in a case that the pressure feedback control is selected, a flow rate increasing control for increasing the flow rate command value after the case with the passage of time is performed.

Abstract: The invention relates to a total power regulation device for two pumps (2, 42), each of which is connected to a working conduit (5, 45). The delivery volume of the pumps (2, 42) can be set separately by a respective adjusting device (6, 46), whereby a control pressure that is active in each adjusting device (6, 46) can be set by a total power regulation valve (18, 58). The latter (18, 58) has a measuring surface (24, 64) of the total power regulation valve (18, 58) of one pump (2, 42) can be directly exposed to the working pressure of the other pump (42, 2).

Abstract: A dual mode control system for a hydraulic circuit (200) having a variable displacement pump (216) includes at least two actuators, each controlled by a respective valve. The valves are connected in series with a pressure sensor (250) measuring a pressure of fluid between the first valve (224) and the second valve (234) and relaying a signal to the electronic controller (202). The electronic controller (202) operates in a first mode, varying the displacement of the pump (216) based on a command signal operating at least one of the valves, and operates in a standby mode, varying the displacement of the pump (216) based on the signal from the sensor, when both valves are in their respective neutral positions.

Abstract: When a mode selection command selects an economy mode, a mode selector 700e is turned on and outputs an engine revolution speed modification value ?N0 (?N1=?N0) computed by an engine-revolution-speed modification value computing section 700d. A subtracter 700f subtracts the engine revolution speed modification value ?N1 from a rated target revolution speed Nmax, thereby computing a target engine revolution speed NR2. The computing section 700d computes the engine revolution speed modification value ?N0 depending on a pump delivery pressure mean value Pm. In a table stored in a memory, the relationship between Pm and ?N0 is set such that when Pm is not higher than PA near a midpoint pressure, ?N0 is 0 and when Pm exceeds PA, ?N0 is increased with an increase of Pm. Thus, the revolution speed of a prime mover is reduced by mode selection so as to improve fuel economy.

Abstract: A rear half part of a surface of a main body of a working oil tank installed in line with a control valve opposing to the valve is dented in an inclining surface shape in the direction moving away from the valve so that between both the tank and the valve, is formed a working space for attaching and detaching a pressure compensating spool, while return tubes are separately connected to the upper and the lower side of a filter case side wall within the body. Within the body, is provided a cylindrical filter case having a bottom in which a return filter for return oil is housed, and the return tubes are connected to the case side wall in a state of communicating with the inside of the filter case.

Abstract: The invention relates to a regulator device (1) for a hydraulic pump which pumps into at least one working pipe (13), and to a valve unit for said pump. The pumping volume of the hydraulic pump (1) is regulated with the aid of a regulator device (15, 19) exposed to a regulating pressure which is regulated by an adjusting valve (26) in conformity to a first and a second pressure. The first pressure passes through a first pressure pipe (38) and acts on a first measuring surface, the second pressure passes through a second pressure pipe (39) and acts on a second pressure surface opposite to the first surface of the adjusting valve (26), the first pressure being higher than the second pressure. Said invention is characterized in that a pressure chamber (45) is arranged between the first and second measuring surfaces, thereby forming a discharge channel towards the second pressure pipe (39).

Abstract: A computing section computes a reference revolution-speed decrease modification amount DNLR; and multiplies an engine revolution speed modification gain KNL by a reference revolution-speed decrease modification amount DNL and then DNLR, to thereby compute an engine revolution-speed decrease modification amount DND based on input change of an operation pilot pressure, which is modified in accordance with DNLR. At the time when a lever operation input from an operation command unit is changed from full stroke to half stroke, if a pump delivery pressure is in a pressure range of a pump absorption torque control region Y where the pump delivery pressure is lower than that in a region X, the reference revolution-speed decrease modification amount computing section 700v computes the modification amount DNLR to be 0, and therefore lowering of a target engine revolution speed with auto-acceleration control is not caused.

Abstract: The invention relates to a hydraulic circuit arrangement for setting the delivery volume of a pump, with an electrically activatable control-valve unit, by means of which, alternately, an active side of a servo system can be acted upon with pressure and, at the same time, its passive side can be relieved to the tank, and with a device for pressure limiting pressure regulation, which comprises pressure limiting valves, by means of which the working lines of the pump can be connected to the servo lines. To reduce the servo pressure load and improve the reaction time, check valves which shut off in the direction of the servo system are provided, by means of which the two servo sides can be connected in each case to the charge pressure via a relief line. Moreover, the device for Pressure limiting pressure regulation comprises an orifice which can be positioned in a line leading to the passive servo side. The invention relates, furthermore, to a method for pressure.

Abstract: Method and arrangement for controlling a work vehicle that includes a hydraulic system (22) having at least one pump (18,180) and at least one actuator (4,5,8,9,10) operatively driven by hydraulic fluid delivered from the pump and at least a first pump (18) is a variable displacement pump. The system (22) is of the load-sensing type in that pump displacement is controlled by a pilot pressure representing a load exerted on the system. The arrangement includes means (63) for reducing the pilot pressure delivered to the first pump (18) so that the first pump displacement is regulated down when there is a need for limiting hydraulic power consumption.

Abstract: An actuator control system is disclosed. The actuator control system may have a pump and at least one actuator. The actuator control system may further have an actuator valve configured to control the at least one actuator. The actuator control system may also have a pump pressure sensor configured to determine a pump pressure value and a load pressure sensor configure to determine a load pressure value. The actuator control system may additionally have a controller configured to receive the pump pressure value and the load pressure value. The controller may further be configured to compare the pump pressure value and the load pressure value, and selectively implement a primary control strategy and a secondary control strategy based on the comparison.

Abstract: On the basis of reference torque and torque correction amount output units (T1 and T2), a torque control command pressure is calculated so that the input torques of first and second pumps are increased. The calculated torque command instruction pressure is then supplied as external command pressure to the varying mechanism of a regulator used for the first and second pumps so as to prevent the input torques of the first and second pumps from being decreased more than necessary. As a result, even when three variable displacement hydraulic pumps are used with the discharge pressure of one of the hydraulic pumps reduced by a pressure reducing valve and further the input torques of the other two hydraulic pumps are decreased by that pressure, the engine output can be efficiently utilized, and the work rate does not decrease.

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: A system and method for controlling shakability of a work tool. A series of input commands from a control unit to the hydraulic pump cause the hydraulic pump to cycle between a first displacement (maximum) at a first rate (maximum) and a second displacement (zero) at a second rate (less than maximum), within a predetermined frequency. Ultimately, the hydraulic pump remains in a partially upstroked position at the beginning of every cycle. Accordingly, within a small fraction of time after upstroking, the pump is capable of providing full flow to the actuators, resulting in much faster response and movement of the actuators, and therefore improved shakability of the work implement.

Abstract: A vane pump for pumping hydraulic fluid wherein fluid at a pressure intermediate the inlet pressure and the outlet pressure of the pump is supplied to under vane passages of the vanes located in and passing through the rise region of the pump. This assists in preventing damage to the vanes caused by driving the vanes through the protective coating of oil on the wall of the pump chamber when the vanes are travelling through an inlet region of the pump.

Abstract: A hydraulic system includes a first pump that delivers hydraulic fluid to a first load outlet point and to a second load outlet point, a second pump that delivers hydraulic fluid to the second load outlet point, but not to the first load outlet point, a pressure detector for detecting the load pressure at the first load outlet point and a pressure detector for detecting the load pressure at the second load outlet point. The system includes a controller for controlling the first pump on the basis of the detected load pressure at the first load outlet point and the detected load pressure at the second load outlet point, and a controller for controlling the second pump on the basis of the detected load pressure at the second load outlet point but not on the basis of the detected load pressure at the first load outlet point.

Abstract: A hydraulic control system is disclosed, which can minimize the flow rate of a hydraulic fluid being discharged from a variable displacement hydraulic pump by using pilot pressure constantly produced by a pilot pump when a switching valve is in a neutral position, and can adjust the flow rate of the hydraulic fluid being discharged from the variable displacement hydraulic pump by using pressure produced by a pressure generator positioned at the most downstream side of a bypass passage if a separate input signal is applied to the pressure generator when the switching valve is operated.

Abstract: Laying apparatus and method for cables, lines, conductors or suchlike. The apparatus comprises at least a hydraulic circuit provided with a variable delivery feed pump and with a motor connected to the feed pump in order to drive laying members for the cables and suchlike. The hydraulic circuit comprises detectors able to detect the value of pressure of the oil inside the hydraulic circuit and to compare it with a pre-determined pressure value, and valves connected to the detectors and able to reduce the delivery of the feed pump in the event that the pressure measured exceeds the pre-determined pressure value.

Abstract: A fluid pump control system for excavators enables fluid pumps to produce hydraulic flows of a quantity great enough to actuate hydraulic actuators for smooth composite operations. The system includes variable displacement fluid pumps, fluid quantity control mechanisms for controlling the discharge quantity of the respective fluid pumps, fluid quantity control signal lines respectively connected to the fluid quantity control mechanisms, signal pressure control lines for bringing the fluid quantity control signal lines into connection with a fluid tank to drop the fluid quantity control signal pressures within the fluid quantity control signal lines, and a plurality of cutoff valves attached to the signal pressure control lines in tandem and shiftable in concert with the shifting movement of spools of a control valve for increasing the fluid quantity control signal pressures within the signal pressure control lines in proportion to the shifting amounts of the cutoff valves.

Abstract: An engine lag down suppressing device of construction machinery, comprising a vehicle body controller (13) having a first torque control means and a second torque control means, and a third torque control means. The first torque control means controls a torque control valve (7) to the minimum pump torque (value: Min) according to a target engine rotational speed (Nr) when the operating device (5) in the non-operated state of an continues for a monitoring time (TX1) to suppress an engine lag down after a specified holing time to hold a torque to a low pump torque is passed when the operating device in the non-operated state is operated. The second torque control means controls the torque control valve (7) to hold the minimum pump torque for a specified holding time (Tx2) after the operating device (5) in the non-operated state is operated.

Abstract: A vehicle is disclosed having a hydraulic system. The hydraulic system includes a pressure regulator that maintains the output pressure from a hydraulic pump above a predetermined minimum pressure.

Abstract: Disclosed is a hydraulic system for utility vehicles, in particular agricultural tractors, for supplying primary and/or auxiliary pressure medium consumers (6, 11, 12) with pressure medium, comprising a pump (1), whose pressure and flow are controlled as a function of the load pressure of the pressure medium consumers by a pressure and flow controller (13) to which whenever auxiliary pressure medium consumers (11, 12) are operating, a higher load pressure compared to the actual load pressure is reported through an amplifier device. In order to obtain rapid response of an actuated auxiliary pressure medium consumer it is proposed that the amplifier device (29) consists of a proportionally controllable pressure reducing valve (39).

Abstract: A hydraulic control system for a working machine according to the present invention comprises a hydraulic pump for supplying working oil to a hydraulic actuator through a control valve, a relief mechanism disposed on the discharge side of the pump, the relief mechanism assuming an open state when a pump discharge pressure which varies according to the pump flow rate exceeds a predetermined pressure and assuming a closed state when the pump discharge pressure becomes the predetermined one or lower, an ordinary control means for controlling the pump flow rate in accordance with working information, and a pressure feedback control means for controlling the pump flow rate in accordance with the pump discharge pressure. In this system, out of controls performed by both control means, control wherein the flow rate by one control becomes smaller than that of the other is selected, thereby opening/closing control of the relief mechanism is performed.

Abstract: A method is described for controlling a hydraulic system, particularly of mobile working machine, with at least one internal combustion engine driving at least one hydraulic pump with adjustable volumetric displacement and possibly additional fixed-displacement pumps.

Abstract: A hydraulic control apparatus is provided to prevent failure that can occur due to hunting, to elevate performance of a hydraulic control valve, and to improve operation efficiency by effectively conducting bleed off. The hydraulic control apparatus can include a first change over valve group that can include a change over valve connected with a first delivery line associated with the variable capacity pump, and arranged to have load sensing function. A second change over valve group can also be provided, and can include at least one change over valve connected with a second delivery line associated with the variable capacity pump. An open and close motion valve and a compensation valve can be configured to constitute a pressure compensation flow control means connected through the second delivery line and the second change over valve group.