Abstract: An outdoor grounds maintenance vehicle is self-propelled by a hydrostatic traction drive system that provides dynamic braking to the vehicle without the need for separate service brakes acting on the wheels of the vehicle. An engine kill device can be manually actuated by the operator to access the dynamic braking of the traction drive system by reducing the speed of the prime mover that powers the pump of the traction drive system. This provides an auxiliary braking system that can be used in an emergency or on demand by the operator in the event the accelerator pedal does not properly control the pump swashplates. The operator can control the rate at which the auxiliary brake system reduces the speed of the prime mover to zero.

Abstract: A hydraulic system comprises: a hydraulic pump that includes an swash plate; an swash plate angle sensor for measuring the angle of the swash plate; an swash plate driving piston for moving the swash plate of the hydraulic pump in response to changes in pressure applied to a large diameter section; an swash plate control hydraulic line for supplying the large diameter section with a portion of the hydraulic oil discharged by the hydraulic pump; a control valve that controls the flow rate of the hydraulic oil that is following into and out of the large diameter section; an electro-proportional pressure reducing valve for producing pilot pressure that is to be transmitted to one side of the control valve; and a control device for controlling the electro-proportional pressure reducing valve according to an operation signal of an operation device and the angle information from the swash plate angle sensor.

Abstract: A method for preventing prime mover stall for a work machine including a hydraulic system having a plurality of control valves served by a hydraulic pump. The method can include determining an actual required flow rate value for the plurality control valves and a total maximum flow rate to the plurality of control valves that will enable the prime mover to operate without stalling. The method can also include operating the plurality of control valves such that the combined total flow of the plurality control valves is at or below the total maximum flow rate such that the pump operates at a condition below which prime mover stall will occur. The method can also include setting a flow sharing allocated specific criteria in which the flow reduction takes place during a flow saturation condition for each of the plurality of control valves such that the total sum of the flow rates (calculated based on the criteria) is equal to or less than the total maximum flow rate.

Abstract: The present invention provides a construction machine equipped with a pressure accumulation device that accumulates return oil from an actuator, and that can implement both improvement in fuel efficiency with enhancement in workability. To achieve the foregoing, a controller sets an actuator upper limit output power that is an upper limit for an output power of the actuator according to a work mode selected by a work mode selection device, and controls a first control valve and a second control valve such that a sum of an output power of a hydraulic pump and an output power of the pressure accumulation device does not exceed the actuator upper limit output power.

Abstract: A hydraulic apparatus has a plurality of pump modules each of which is formed by a plurality of working chambers having a common high pressure manifold. A connecting circuit switchably connects pump modules to first and second hydraulic circuit portions to allocate capacity as first and second demands for hydraulic fluid vary. In an apparatus which may have two or more connecting circuit outputs, valves may be controlled or working chamber pumping cycles made inactive to facilitate the reallocation of a pump module from one output to another, and a control strategy addresses pump module allocation when the demands for hydraulic fluid exceed available capacity.

Abstract: A condenser fan assembly includes a first condenser fan and a first motor coupled to the first condenser fan via a first shaft, where the first motor is configured to drive rotation of the first condenser fan via the first shaft, and a second condenser fan and a second motor coupled to the second condenser fan via a second shaft, where the second motor is configured to drive rotation of the second condenser fan via the second shaft. The condenser fan assembly also includes a fan rotation restrictor configured to selectively block and enable rotation of the first shaft.

Abstract: A preselection valve is for a hydraulic valve assembly with a switching element, a pressure input line, a first pressure output line and a first load pressure line with a load pressure inlet and output. The switching element is switchable from neutral to a first switching position. The pressure input line is connected to the first pressure output line in the first position. The preselection valve has a second and third load pressure line and a load pressure increasing device. The second load pressure line branches off the pressure input line upstream of the switching element. The load pressure increasing device is connected to the third load pressure line, which connects the pressure increasing device to the first load pressure line. The second load pressure line is connected to the pressure increasing device in the first switching position and the second load pressure line is blocked in the neutral position.

Abstract: A method of controlling a rotatable load by a hydraulic system, the method includes determining if the hydraulic system is in a first operating state or a second operating state; controlling the rotatable load in a valve control mode if the hydraulic system is in the first operating state, the valve control mode including controlling the rotatable load by controlling a valve arrangement; controlling the rotatable load in a displacement control mode if the hydraulic system is in the second operating state, the displacement control mode including controlling the rotatable load mainly by controlling the displacement of a hydraulic machine; and applying a non-zero absolute minimum displacement limitation to the hydraulic machine at least in the valve control mode.

Abstract: Methods and systems for controlling a hydromechanical transmission are proposed. In one example, a control method for a hydrostatic unit of a hydromechanical variable transmission (HVT) is presented, comprising controlling the hydrostatic unit via a feedforward control architecture including a non-linear, multi-coefficient model, wherein the hydrostatic unit comprises a hydrostatic pump and a hydrostatic motor. A desired differential pressure of the hydrostatic unit or a desired hydraulic pump displacement may be used as inputs for the model, where the model's output is a pressure difference for a pump control piston coupled to a swash plate of the hydrostatic unit. Use of the non-linear model permits the hydrostatic unit to be controlled based on load, speed, and/or torque, thereby increasing the adaptability of the control system.

Abstract: An inching system for a vehicle having a hydrostatic transmission and an engine that drives the transmission. The transmission has a pilot pressure port with a pressure of hydraulic fluid at the pilot pressure port controlling a level of power from the transmission, a beginning of draining of the hydraulic fluid from the pilot pressure port defining an inching starting point. The system includes a brake pedal and an electrohydraulic valve coupled to the pilot pressure port of the transmission, the valve being configured to drain the hydraulic fluid at the pilot pressure port. A sensor is coupled to the pedal to detect an input from the operator, the sensor producing a signal indicative of the input from the operator. A controller receives the signal and a speed of the engine. The controller controls the electrohydraulic valve dependent upon the signal and the engine speed so that the inching starting point is unchanged regardless of the speed of the engine.

Abstract: A system and method for measuring a speed of an engine are provided. The engine has a positive displacement pump drivingly connected to a rotor shaft thereof, the pump having an inlet for receiving a fluid supply and an outlet for outputting pressurized fluid. A sensor signal is received from a pressure sensing device provided at an inlet of the pump, the sensor signal comprising a series of periodic oscillations. A frequency of the oscillations is determined, the frequency proportional to a rotational speed of the rotor shaft. The speed of the engine is then determined from the frequency of the oscillations and the speed of the engine as determined is output for controlling operation of the engine.

Abstract: A work vehicle a computing system configured to receive first and second input associated with controlling the operation of the first and second hydraulic load, respectively. Furthermore, the computing system is configured to control the operation of a first or second flow control valve corresponding to the one of the first or second hydraulic loads associated with the greater hydraulic fluid pressure such that the corresponding adjustable orifice is at a maximum flow position. Additionally, the computing system is configured to determine the first and second pressures of the hydraulic fluid being supplied to the first or second hydraulic loads. Moreover, the computing system is configured to control the operation of the first or second flow control valve corresponding to another of the first or second hydraulic loads based on the corresponding received first or second input and the determined first and second pressures.

Abstract: A method of autonomously controlling the ground speed of a harvester, such as a self-propelled or towed wind rower, uses both the engine speed and the header speed as control parameters to increase or decrease the ground speed as necessary to maintain efficient harvester operation over varying terrain and crop conditions. A control system includes a controller which receives signals from sensors indicative of engine speed, header speed and harvester ground speed and uses actuators to control the header speed, engine speed and harvester ground speed. An operator interface permits an operator to engage or disengage the autonomous mode of control system operation, as well as to directly control the harvester.

Abstract: A control system for a vehicle uses one or more inputs of a velocity request, a brake request, a speed request, travel direction indication, engine speed, and vehicle speed to determine a control strategy for a continuously variable transmission. A target engine speed is selected based upon the inputs, and the engine and continuously variable transmission ratio are controlled to achieve the target engine speed while controlling the vehicle according to the inputs. In some embodiments, the control strategy further selects the target engine speed according to accessory system demands, such as a hoist or lift system.

Abstract: Hydraulic systems and methods comprising a source of hydraulic pressure; a hydraulic load; and an energy recovery circuit. The source of hydraulic pressure is fluidly connected to the hydraulic load through a first hydraulic channel with an orifice. The energy recovery circuit includes a recovery channel which is fluidly connected at its first end to the orifice on the side of it which is connected to the source of hydraulic pressure, and which is fluidly connected at its second end to a hydraulic motor.

Abstract: A road milling machine includes a machine frame, at least three travelling devices, a milling drum, and at least one hydraulic drive system. The hydraulic drive system includes at least one hydraulic pump, at least one hydraulic fixed displacement motor for driving at least one driven travelling device, and one each hydraulic variable displacement motor for driving the remaining travelling devices. A first gearbox is arranged between the fixed displacement hydraulic motor and its associated travelling device. One each second gearbox is arranged between each of the hydraulic variable displacement motors and their associated travelling devices. The transmission ratio of the first gearbox is lower than the transmission ratios of the second gearboxes and/or the displacement volume of the fixed displacement motor is smaller than the maximum displacement volume of the variable displacement motors.

Abstract: The working machine includes a traveling device, a traveling motor, a hydraulic pump including a swashplate, a prime mover to drive the hydraulic pump, a first servo-cylinder to set an angle of the swashplate, a charge pump to supply pilot fluid to the first servo-cylinder, a switching valve shiftable between a traveling position to supply the pilot fluid from the charge pump to the first servo-cylinder and a neutral position to stop the pilot fluid supply to the first servo-cylinder, a switching operation member operable to select either a traveling mode or a neutral mode, and a controller to shift the switching valve between the traveling position and the neutral position. The controller holds the switching valve at the neutral position after the switching operation member is operated to select the traveling mode until a rotation speed of the prime mover becomes not less than a first predetermined rotation speed.

Abstract: In a hydraulic system, such as for a tractor or other agricultural vehicle, a main supply pump supplies fluid to a steering system through a steering circuit and a second pump supplies fluid to a cooling fan motor. The second pump is connected with the steering circuit to provide a second a source of fluid to the steering system when the main supply pump is unable to meet demand. A prioritization valve regulates the flow of fluid from the second pump to the motor. The second pump acts as a secondary pump for the steering system and drives a cooling fan.

Abstract: An in-vehicle motor-driven compressor includes a temperature rise estimator configured to estimate a temperature rise of the diode based on an expected reverse current, an on-voltage of the diode, and a heat resistance of the diode. The in-vehicle motor-driven compressor further includes a rotation speed controller configured to set a rotation speed limit of the electric motor, based on the estimated temperature rise of the diode so that a temperature of the diode does not exceed a junction temperature of the diode even when the electric motor is stopped and the reverse current flows through the diode, and limit a rotation speed of the electric motor to lower than or equal to the rotation speed limit.

Abstract: A shovel includes a lower traveling body, an upper rotating body, an attachment including a boom and an arm, a controller, an engine, and a hydraulic pump that is driven by the engine and discharges hydraulic oil to drive the attachment. The controller is configured to obtain a hydraulic load applied to the attachment and calculate an engine speed command at predetermined time intervals based on the obtained hydraulic load.

Abstract: A work machine includes an engine, a pilot pump to be driven by the engine to supply a pilot fluid, an operation pump to receive a first pilot fluid to change an output power in accordance with the first pilot fluid, a pilot fluid tube provided between the pilot pump and the operation pump, an operation valve connected to the pilot fluid tube to output the first pilot fluid, the first pilot fluid being a part of the pilot fluid supplied from the pilot fluid, a temperature sensor to measure a temperature of at least one of an operation fluid including the pilot fluid, a cooling water, an engine oil, and an outside air, and a pressure controller to control a first pilot pressure of the pilot fluid outputted from the operation valve when a temperature measured by the temperature sensor is equal to or higher than a first temperature.

Abstract: A combination of a towing vehicle and an agricultural harvesting machine drawn by the towing machine is provided. The harvesting machine includes at least one working assembly for conveying crop (G), for processing crop (G) or both. The harvesting machine also includes a working connection to the towing vehicle in order to be supplied with drive power by the towing vehicle in order to operate the at least one working assembly and a control device can be operated in a harvesting mode in order to specify a ground speed (v) for the combination depending on ascertained operating parameters of the harvesting machine and the towing vehicle.

Abstract: In a work machine including a hydraulic pump (1), a swing motor (2), and swing relief valves (3a and 3b), the amount of the swing operation (P1) related to the swing motion of the swing motor (2) is detected, and the hydraulic pressure (P2) supplied from the hydraulic pump (1) to the swing motor is also detected. Additionally, the required flow rate (FR) of hydraulic oil required for the swing motor (1) is set based on the amount of the swing operation (P1). In addition, the volume of relief (FE) is estimated from the hydraulic pressure (P2) based on the override characteristics of the swing relief valves (3a and 3b). The discharge flow rate of the hydraulic pump (1) is controlled based on the value obtained by subtracting the volume of relief (FE) from the required flow rate (FR).

Abstract: A vehicle includes a transmission housing disposed on a frame to independently drive a pair of wheels. The transmission includes first and second motor having collinear motor shafts and first and second pump hydraulically connected to the respective motors and having collinear pump shafts. An input shaft extends into the housing and drives both pump shafts and has an axis of rotation that is perpendicular to the pump shaft axes of rotation.

Abstract: A method for operating a working machine provided with a power source providing power and a plurality of power consuming systems connected to the power source includes the steps of providing a model predicting a power demanded by at least one of the power consuming systems, detecting at least one operational parameter indicative of a power demand, using the detected operational parameter in the prediction model, and balancing a provided power to the demanded power according to the prediction model.

Abstract: A hydraulic linear actuator system known as the “Dynaco Stepper Pump Hydraulics System” is which is an electrically driven hydraulic pump system made of durable materials for use in an electronically controllable hydraulic system comprised of: (a) an electrically driven stepper motor; (b) a hydraulic pump to pressurize a hydraulic fluid; (c) a means to connect the stepper motor to the hydraulic pump; (d) a pressurized reservoir for a quantity of hydraulic fluid; (e) a means to supply pressurized fluid to a hydraulic actuator; (f) the hydraulic actuator with a means to provide linear motion to an object; (g) the means to provide linear motion to an object; (h) a means to return lowered pressurized fluid to the reservoir. An alternative embodiment is further comprised of a controller with a series of feedback signals.

Abstract: A method of controlling a pump and motor system having at least one of a variable displacement pump and a variable displacement motor. The method may comprise providing an engine drivingly coupled to a primary load and a secondary load, the secondary load being driven by the pump and motor system. The method may also comprise sensing a change in engine speed in response to a change in the primary load. The method may further comprise changing the engine speed to compensate for the primary load change. The method may further comprise changing a displacement of the at least one variable displacement pump and the variable displacement motor to maintain a constant secondary load.

Abstract: In an engine-overrun-preventing control device, if an engine speed exceeds a maximum speed, a minimum value of an inching rate is set such that higher the actual engine speed results in a higher minimum value of an inching rate. The hydraulic pump displacement is adjusted to obtain a higher inching rate between the minimum value of the inching rate and an inching rate set based on a brake stroke. If the engine speed exceeds a commanded speed and a pressure time-rate-of-change at the pump intake exceeds a prescribed value, the minimum value of the inching rate is set such that the higher the pressure time-rate-of-change, the higher the minimum value of the inching rate. The pump displacement is adjusted to obtain a higher inching rate between the minimum value of the inching rate set based on the pressure time-rate-of-change and the inching rate set based on the brake stroke.

Abstract: A machine having a pump overspeed protection system operating thereon includes an internal combustion engine, a plurality of ground engaging elements, and a drivetrain coupling the internal combustion engine and the ground engaging elements. The drivetrain includes a torque converter having a locked configuration and an unlocked configuration. The machine also includes a plurality of pumps driven by the internal combustion engine. An electronic control is in communication with the internal combustion engine, the torque converter, and the plurality of pumps.

Abstract: A control system is provided to control the rate of pressure rise in a hydraulic lift and flotation system. When a hydraulic cylinder of the hydraulic lift and flotation system is to be adjusted, the pressure in the hydraulic lift and flotation system has to be increased to a predetermined pressure controlled by a relief valve before the hydraulic cylinder can be operated. The unload valve of the hydraulic lift and flotation system can be closed in a controlled or regulated manner in order to control the rate at which pressure rises in the hydraulic lift and flotation system.

Abstract: A hydraulic system includes an engine driven adjustable hydraulic pump which supplies fluid to a hydraulic consumer, and an electronic control unit. The adjustable pump includes flow controller for controlling a pressure difference between the consumer and the adjustable pump to a pre-determined control pressure difference. The flow controller includes an actuator controlled by the control unit, through which the pressure difference can be controlled. The electronic control unit receives an engine speed signal and controls the actuator to control the pressure difference, in order to make power delivery of the adjustable pump conform to the operating conditions of a vehicle.

Abstract: A hydraulic load ramping system, in certain aspects, may utilize load sensing feedback from an engine, thereby reducing the possibility of overloading the engine as well as smoothing the transition between hydraulic load levels. In particular, by ramping between hydraulic load levels, unwanted movement of hydraulically-driven equipment may be minimized. In addition, by efficiently monitoring the load sensing feedback and ramping between hydraulic load levels, the hydraulic output may be maximized.

Abstract: A hydraulic system includes an engine driven variable displacement hydraulic pump which supplies fluid to a hydraulic consumer and an electronic control unit. A flow rate adjusting unit includes a stop that can be brought into engagement with an adjusting piston. In order conform the power output of the pump to the operating conditions of the vehicle, the stop of the flow rate adjusting unit includes adjusting devices that can be controlled by the control unit, so that the maximum flow rate of the pump can be varied by the electronic control unit. The electronic control unit generates a control signal for the adjusting device as a function of a sensed engine speed.

Abstract: A lubrication system is provided that includes a pump operatively connected to one or more supply lines for delivery of a lubricant, the system including a first pressure sensor associated with the supply line at a first position, and a second pressure sensor associated with the supply line at a second position downstream of the first position and pump, a controller configured to receive pressure signals and control operation of the pump based upon the pressure differential between the pressures at the first position and second position. The pressure differential may be employed to determine when a pressure at a third position downstream of the second position has been achieved. At least one of the pressure sensors may be positioned adjacent to the pump, the controller further being operable to deactivate the pump in the event that a maximum pump pressure has been met.

Abstract: Torque control for a construction machine three-pump system that can accurately control the total absorption torque of first, second, and third hydraulic pumps and effectively use the output torque of an engine. A pump base torque computation section 42 calculates a pump base torque Tr from a target rotation speed. A subtraction section 44 calculates a reference value Tf for the maximum absorption torque available to the first and second hydraulic pumps 2, 3 by subtracting a third pump reference absorption torque T3r from the pump base torque Tr. A correction torque computation section 45 calculates a correction torque value from the delivery pressure of the third hydraulic pump 4. An addition section 46 calculates a target absorption torque Tn by adding the correction torque value Tm to the reference value Tf. A first regulator 31 is controlled so as to obtain the target absorption torque Tn.

Abstract: A control method for a hydraulic type continuously variable transmission for suppressing a harmful effect due to the reacceleration just after deceleration of a vehicle. In a hydraulic type continuously variable transmission, the operation of a shifting actuator is stopped to suspend the shift control (S7) when a throttle valve is rapidly opened just after fully closed (S4: Yes) and an engine speed NE [rpm] is being rapidly increased (S6: Yes). Accordingly, even when the actual engine speed NE becomes much greater than a target engine speed T_NE during reacceleration just after deceleration of a vehicle, unexpected shift control (upshifting) can be prevented, so that more desirable torque can be produced.

Abstract: The described system and method allow a controller to calibrate a transmission variator of a continuously variable transmission for torque control by obtaining static and dynamic qualities and parameters of the variator through an automated calibration procedure. The system and method employ a pair of transmission mode configurations and operational configurations in combination to obtain system-specific information. In this way, the system is able to calibrate out the system variations to provide effective feed forward torque control of the continuously variable transmission. In an embodiment, a first calibration operation is performed while the transmission is neutralized and a second calibration operation is performed while the transmission is engaged in a mode providing a fixed variator output speed.

Abstract: An engine lag down control system for construction machinery has a machinery body controller having first, second and third torque control units and a solenoid valve. The first torque control unit controls a torque control valve to a minimum pump torque corresponding to a target number of engine revolutions when a non-operated state of a control device has continued beyond a monitoring time. The second torque control unit controls the torque control valve such that the above-described minimum pump torque is held for a predetermined holding time subsequent to the operation of the control device from the non-operated state. The third torque control unit controls the torque control valve such that from a time point of a lapse of the predetermined holding time, the pump torque is gradually increased on a basis of a predetermined torque increment rate.

Abstract: A load control structure for a work vehicle comprises: set rotation speed detection device for detecting a set rotation of an engine of the work vehicle; actual rotation speed detection device that senses an actual rotational speed of the engine; continuously variable speed change device that receives power from an engine of the work vehicle; speed change position detecting device for detecting a speed change operation position of the continuously variable speed change device; operating device for speed-shifting the continuously variable speed change device; control device for controlling the operation of the operating device; wherein the control device calculates a drop amount of the actual engine rotation speed from the set rotation speed based on the detected information from the set rotation speed detection device and the actual rotation speed detection device, and sets a limit operation position for the continuously variable speed change device based on the calculated drop amount and a correlation data t

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: A pump control apparatus for a hydraulic work machine includes: a rotation speed setting device that sets a target rotation speed for an engine; a rotation speed control device that controls an engine rotation speed so as to adjust the engine rotation speed to the target rotation speed; a first variable hydraulic pump used to drive a work hydraulic actuator, driven by the engine; a second variable hydraulic pump used to drive a cooling fan, driven by the engine; and a pump control device that controls an output flow rate of the first variable hydraulic pump and an output flow rate of the second variable hydraulic pump so as to ensure that a sum of an intake torque of the first variable hydraulic pump and an intake torque of the second variable hydraulic pump does not exceed an engine output torque determined in advance based upon the target rotation speed.

Abstract: A fixed displacement binary pump is provided for a powertrain on a vehicle. A hydraulic system is operatively connected with first and second discharge ports of the pump and is operable to alternately permit fluid flow through both discharge ports (i.e., full displacement or volumetric output of the pump) or permit flow through only the first discharge port (i.e., partial displacement or volumetric output of the pump). The pump may be packaged in a front support of the transmission. An auxiliary pump may be provided that is operable to supplement the output of the binary pump or to be used when the binary pump is off. A method of operating the binary pump and auxiliary pump is provided.

Abstract: A load control structure for a work vehicle comprises: set rotation speed detection device for detecting a set rotation of an engine of the work vehicle; actual rotation speed detection device that senses an actual rotational speed of the engine; continuously variable speed change device that receives power from an engine of the work vehicle; speed change position detecting device for detecting a speed change operation position of the continuously variable speed change device; operating device for speed-shifting the continuously variable speed change device; control device for controlling the operation of the operating device; wherein the control device calculates a drop amount of the actual engine rotation speed from the set rotation speed based on the detected information from the set rotation speed detection device and the actual rotation speed detection device, and sets a limit operation position for the continuously variable speed change device based on the calculated drop amount and a correlation data t

Abstract: A hydraulic system includes an engine driven variable displacement hydraulic pump which supplies fluid to a hydraulic consumer and an electronic control unit. A flow rate adjusting unit includes a stop that can be brought into engagement with an adjusting piston. In order conform the power output of the pump to the operating conditions of the vehicle, the stop of the flow rate adjusting unit includes adjusting devices that can be controlled by the control unit, so that the maximum flow rate of the pump can be varied by the electronic control unit. The electronic control unit generates a control signal for the adjusting device as a function of a sensed engine speed.

Abstract: A device for use in a work vehicle such as a wheel loader, capable of reliably preventing engine stall due to rapid application of high hydraulic load, without causing problems such as deterioration in fuel efficiency or vehicle performance and waste of energy. When determining that an engine speed detected by the engine speed detecting sensor has been decreased to the threshold value or lower, the controller implements a control to reduce the absorption torque of the variable displacement hydraulic pump. The hydraulic load is thus shifted to a low hydraulic load line. The change of the hydraulic load from the high hydraulic load to the low hydraulic load gives a margin to the current torque of the engine with respect to the low hydraulic load. Consequently, the actual speed of the engine is increased to return onto the regulation line, exceeding the threshold value.

Abstract: A hydraulic control system for a machine is disclosed. The hydraulic control system may have a source driven by an engine to pressurize fluid, and a tool actuator movable by pressurized fluid. The hydraulic control system may further have a first valve element movable to control an amount of pressurized fluid directed to the tool actuator, and an interface device movable by an operator to control an amount of pressurized fluid directed to move the first valve element. The hydraulic control system may also have a second valve element movable to limit an amount of pressurized fluid available to move the first valve element, and a controller in communication with the second valve element. The controller may be configured to move the second valve element to reduce pressurized fluid directed to the first valve element in an amount related to a load on the engine.

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: A load control device for an engine of a work vehicle that purposes to render the work vehicle, such as a wheel loader or the like, capable of raising a vehicle speed in a short period of time by providing a sufficient traction force when a high traveling load is imposed, without causing degradation of a vehicle body performance, waste of energy, and other problems. The load control device is provided with variable displacement hydraulic pumps (7, 8, 9) being provided with absorption torque changing means (19, 22) for changing absorption torque. A controller (18) determines whether a traveling load is in a high state, and when it has been determined that the traveling load is in the high state, control for lowering the absorption torque for the hydraulic pumps (7, 8, 9) is carried out. This control is carried out, provided, for example, that a “power mode” is selected with the power mode switch (31).

Abstract: A hydrostatic system and method of operation thereof, wherein at least one of a fluid motor and a pump of the system has a displacement which is variable for controlling a speed of operation of the motor, the pump being driven by an engine, and a controller configured for monitoring the speed of operation of the motor and an operating characteristic of the engine and automatically controlling the displacement responsive thereto, wherein if the operating characteristic is indicative of engine performance above a predetermined threshold, the controller will control the displacement for maintaining the speed of operation of the motor at about a predetermined value, and, if the operating characteristic is indicative of engine performance below the threshold, the controller will hold the displacement at a constant value. As a result, the controller can prevent the system from further decreasing the engine performance.

Abstract: A method for reducing a torque load associated with an implement includes determining a speed associated with a power source, wherein the power source is configured to provide power to a hydraulic pump, determining a position associated with an implement system, and limiting a flow associated with the hydraulic pump based on the speed associated with the power source and the position associated with the implement system.