Abstract: A method for controlling the rotational speed (S) of an electric motor driven air compressor (2) that supplies compressed air to a pneumatically operated system (5) of a vehicle (1), characterized by the preliminary steps of: a) determining the efficiency (e) of the air compressor (2) for different values (Si) of the rotational speed (S) of the air compressor (2), the efficiency (e) of the air compressor (2) corresponding to the ratio between the pneumatic power (PI) produced by the air compressor (2) and the power (PO) given to the air compressor (2); b) determining one or several specific values (S2, S4) among said different values (Si), for which the efficiency (e) of the air compressor (2) is higher than a threshold value (emin) and/or comparatively higher than those determined for values (SI, S3) close to said specific value(s) (S2, S4); the preliminary steps a) and b) being preferably implemented only once; and characterized by the further repetitive steps of: c) determining the air consumption rate of

Abstract: A mobile surface maintenance machine embodiment includes a mobile body, a solution tank for containing a cleaning fluid, wheels for supporting the mobile body, a maintenance tool(s), an output channel, an electric power source, a first electric motor, and a pressure washer. The pressure washer includes a spray wand, a pressure pump, and a second electric motor. The pressure pump is fluidly coupled to the spray wand and to the solution tank. The pressure pump is configured to pressurize the cleaning fluid supplied to the spray wand. The second electric motor is operatively coupled to and configured to drive the pressure pump. The second electric motor is configured to receive electric power from the electric power source and is commonly powered by the electric power source that provides power to the first electric motor. The second electric motor is separate from the first electric motor.

Abstract: A pressure washer system includes a fluid pump having a fluid inlet and a fluid outlet. A flow sensor is in fluid communication with one of the fluid inlet and the fluid outlet. An internal combustion engine is in driving communication with the fluid pump. A control module is mounted to the fluid pump. The control module is configured to receive an indication of flow through the fluid pump and to control a starting operation of the internal combustion engine to start the internal combustion engine in response to receiving the indication of flow through the fluid pump when the internal combustion engine is not running.

Abstract: A hydraulic system includes an engine; at least one hydraulic pump operatively coupled to the engine for transfer of mechanical power therebetween; and a controller operatively coupled to the engine and the at least one hydraulic pump. The controller is configured to determine a lug speed error as a difference between a target lug speed value and a speed of the engine, set at least one closed-loop gain to a non-zero value when the speed of the engine is less than the target lug speed value, and generate a pump control signal by scaling the lug speed error by the at least one closed-loop gain.

Abstract: The work vehicle includes: a clutch device including a forward-travel clutch and a backward-travel clutch configured to cause, when being in an engagement state, the work vehicle to travel in a forward travel direction and a backward travel direction; a forward-backward travel instruction device configured to instruct the work vehicle to travel in the forward travel direction or the backward travel direction; a clutch state detection device configured to detect whether the forward-travel clutch and the backward-travel clutch are each in the engagement state; and a torque restriction section configured to restrict a maximum absorbing torque of the hydraulic pump to be low when a restriction condition holds, the restriction condition including a condition that a traveling direction of the work vehicle, which corresponds to an engagement state of the clutch device, and a traveling direction of the work vehicle, which is instructed by the forward-backward travel instruction device are opposite to each other.

Abstract: An hydraulic system for a working machine, the system comprising an engine, and an engine speed sensor configured to detect the engine speed; a travel pump configured to actuate a travel actuator, and a travel pump pressure sensor configured to detect the travel pump pressure; a service pump configured to actuate a service actuator, and a service pump pressure sensor configured to detect the service pump pressure; and a micro-controller unit configured to receive input values from each sensor, and configured to determine whether each input value is within a predetermined range where the engine will not stall. The micro-controller unit is configured to provide an output when at least one input value is outside the predetermined range.

Abstract: A method of detecting surging in a turbocharger provided for an internal combustion engine, includes: a first characteristic quantity calculation step of calculating a first characteristic quantity in at least one first frequency region corresponding to at least one first peak frequency component unique to the time of occurrence of surging in the turbocharger on the basis of a time-variable waveform indicating a time-series change of a rotation speed of the turbocharger; a second characteristic quantity calculation step of calculating a second characteristic quantity in a second frequency region including the at least one first frequency region on the basis of the time-variable waveform; and a detection step of detecting surging in the turbocharger on the basis of a relationship between the first characteristic quantity and the second characteristic quantity.

Abstract: In a method of controlling a main control valve in construction machinery, a first joystick signal for controlling a first control valve device and/or a second joystick signal for controlling a second control valve device are received from one joystick. While one of the first and second control valve devices operates, whether or not a joystick signal for controlling another of the first and second control valve devices is inputted is determined. A weighted value is applied to a threshold of valve operation initiation with respect to a joystick displacement to determine a raised threshold of valve operation initiation. If the inputted joystick displacement satisfies the raised threshold of valve operation initiation, a valve stoke corresponding to the inputted joystick displacement is calculated and outputted.

Abstract: An electrically-operated hydraulic work machine drives an actuator with a hydraulic pump driven by an electric motor and exercises load sensing control by controlling the rotation speed of the electric motor. The useful life of an electrical storage device, which is an electrical power source for the electric motor, is increased by suppressing the horsepower consumption of the hydraulic pump. This prolongs the operating time of the electrically-operated hydraulic work machine, and reduces the size of the electric motor. A controller exercises load sensing control over a variable displacement main pump by controlling the rotation speed of the electric motor, and provides the main pump with a torque control device that reduces the delivery rate of the main pump when the delivery pressure of the main pump increases, or provides the controller with a control algorithm that performs the same function as the torque control device.

Abstract: The present disclosure provides a pressure peak reduction valve for an excavator. The pressure peak reduction valve includes at least: a poppet seat which has an inlet port, and at least one communication hole which communicates with a hydraulic tank and is formed in an outer circumferential surface of the poppet seat; a main poppet which slides in the poppet seat; a poppet spring which is provided in the main poppet; a valve seat which has one end portion inserted into the main poppet so as to be in contact with one end portion of the poppet spring; a cone which is provided to be inserted into an openable hole formed at an end portion of the valve seat; an adjustment screw which is provided in the valve seat; and a piston which slides in the adjustment screw.

Abstract: A posture computing apparatus for a work machine includes a detection apparatus that is provided to the work machine and detects angular velocity and acceleration; a first posture angle computing unit that is provided to the detection apparatus and obtains a posture angle of the work machine from the angular velocity and the acceleration detected by the detection apparatus; a low-pass filter that allows the posture angle obtained by the first posture angle computing unit to pass therethrough to output the posture angle as a first posture angle; a second posture angle computing unit that outputs, as a second posture angle, a posture angle obtained from the angular velocity and the acceleration detected by the detection apparatus; and a selecting unit that outputs the first posture angle and the second posture angle in a switching manner, based on information about a change in an angle of the work machine.

Abstract: The invention relates to a side-channel pump and to a method for operating a side-channel pump in which an impeller rotates in a working chamber provided with a side channel. According to the invention, the pump is operated at an overspeed with a gas-filled working chamber in a first step. The speed is then reduced to an operating speed in order to pump a liquid. The pump according to the invention has a high suction power as a result of the overspeed, but only gas is drawn initially.

Abstract: A posture computing apparatus for a work machine includes a detection apparatus that is provided to the work machine and detects angular velocity and acceleration; a first posture angle computing unit that is provided to the detection apparatus and obtains a posture angle of the work machine from the angular velocity and the acceleration detected by the detection apparatus; a low-pass filter that allows the posture angle obtained by the first posture angle computing unit to pass therethrough to output the posture angle as a first posture angle; a second posture angle computing unit that outputs, as a second posture angle, a posture angle obtained from the angular velocity and the acceleration detected by the detection apparatus; and a selecting unit that outputs the first posture angle and the second posture angle in a switching manner, based on information about a change in an angle of the work machine.

Abstract: During a swing start, a pump torque calculating section associated with pump delivery pressure, a pump torque calculating section associated with swing operation pressure, and a maximum value selecting section of a controller perform control to change a maximum absorption torque of a second hydraulic pump between Tb and Tc in accordance with a delivery pressure of the second hydraulic pump. In an operation combining swing with other motion, a subtraction section performs a calculation to subtract a maximum absorption torque Tp2 of the second hydraulic pump from a total pump torque Tr0 to thereby distribute an amount of torque reduced in the second hydraulic pump to a first hydraulic pump associated with an actuator other than a swing motor. Further, a required flow rate can be supplied to the swing motor, thus achieving a smooth shift to a constant speed swing.

Abstract: An apparatus for diverting the flow of wastewater in a lift station, or other liquid storage tank, along the interior wall of the station. In particular, wastewater introduced into a lift station by an inlet is directed by piping so it is discharged along the interior wall to impart a generally circular or vortex-like movement of the wastewater in the station. This generally circular or vortex-like movement prevents coagulation of solids not removed from the station by the pumps therein, reducing the need for cleaning and other maintenance of the lift station.

Abstract: A vacuum generation system, in particular for applications to hybrid-drive motor vehicles, comprises a vacuum pump arranged to be independently driven by either an internal combustion engine (11) or an electric motor (12) depending on the vacuum conditions in utilising devices (15) and the operating conditions of the internal combustion engine. A pump for use in such a system and a method of vacuum generation by using the system are also provided.

Abstract: Air compressor systems, upgrade kits, computer readable medium, and methods for controlling an air compressor for improved performance. The methods may include receiving a working air requirement; determining an estimated air pressure of the air compressor to deliver the working air requirement; measuring a pressure of the air compressor; comparing the measured pressure with the calculated estimated air pressure; if the measured pressure of the air compressor is greater than the determined estimated air pressure by a predetermined greater amount, then decreasing an output control of the air compressor; and if the measured pressure of the air compressor is less than the calculated estimated air pressure by a predetermined lesser amount then increasing the output control of the air compressor. The air compressor may be controlled based on a measured pressure of delivered working air. An oil control system may shut off oil to parts of the air compressor.

Abstract: A controller for a vehicle pneumatic system loads a compressor responsive to engine power absorption by the engine and air storage facility air pressure readings up to a pressure limit. The controller is responds to power demand on the engine in excess of an engine speed related global maximum and air pressure readings down to a global minimum for unloading the compressor. The controller provides for loading and unloading the compressor to maintain storage facility pressure within an operating maximum and an operating minimum which lie between the global maximum and global minimum pressures. The controller responds to air pressure readings reaching or falling below the global minimum for loading the compressor and to air pressure readings reaching or exceeding the global maximum for unloading the compressor.

Abstract: A motor drive device and a motor drive method for a vehicle electric pump. The device and the method set a target value according to an instruction value of a motor control amount and control the motor of the vehicle electric pump based on the target value. When the instruction value is greater than an actual control amount, the instruction value is set to the target value. Meanwhile, when the instruction value is less than the actual control amount, the actual control amount is set to the target value when the actual control amount is less than a value less than a previous target value by a predetermined value, and the value less than previous target value by predetermined value is set to the target value of this time when the actual control amount is greater than the value less than previous target value by predetermined value.

Abstract: Provided is a construction machine including an engine, a hydraulic pump with a supercharger, and a hydraulic actuator, being capable of attaining both of a quick rise of engine speed and an operation of the hydraulic actuator during the rise of the engine speed. The construction machine further includes a supercharging pressure detector to detect a supercharging pressure of the supercharger and a controller to control absorption torque of the hydraulic pump, namely, pump torque. Until engine speed of the engine reaches target engine speed, the controller calculates target pump torque from a predetermined relationship between engine no-load speed and the target pump torque, corrects the target pump torque so as to make it smaller as the detected supercharging pressure is lower, and limits actual pump torque to the corrected target pump torque, until engine speed reaches target engine speed from engine speed lower than the target engine speed.

Abstract: A method and apparatus is provided for starting and stopping a high pressure spray washer having a combustion engine driving a pump to provide high pressure fluid to a spray gun activated by a trigger. Pulling the trigger causes water to flow through the nozzle and pump and a sensor by the pump sends a flow start signal to a control module that activates an electric starter when an engine switch is turned on, thus starting the engine when it wasn't running. When the trigger is released flow to the pump stops and the sensor sends a flow stop signal to the control module. If a predetermined time passes before the sensor detects fluid flow to the pump as occurs when the trigger is pulled, then the engine is shut off. The time can be varied to adjust the time between releasing the trigger and shutting off the engine.

Abstract: A method is provided for regulating fluid pump pressures by detecting an elevation differential between a fluid flow control device and the distal end of a fluid line in communication with the fluid flow control device. A fluid flow control device, for instance a peritoneal dialysis device, is at a first height, a distal end of a fluid line is at a second height, and a valved outlet, when open, affords communication between the fluid flow control device and the distal end of the fluid line. The elevation differential is correlatable with a pressure measurable during a calibration procedure provided as a part of the methodology.

Abstract: A pressure washer device or system that includes various control protocols associated providing an engine powered pressure washer that is convenient to operate and configured for multiple desired uses. The control protocols are preferably configured to maintain the operational integrity of the engine and pump of the pressure washer if undesirable operating conditions, such as a low oil level condition or low water flow conditions, occur during use of the pressure washer.

Abstract: A fluid sprayer is provided and includes a fluid pump assembly having an outlet path and a motor assembly configured to drive the fluid pump assembly to pressurize fluid. The motor assembly is controlled by a throttle mechanism. The fluid sprayer also includes a fluid pressure control assembly including a mechanical pressure transducer configured to be displaced as a function of fluid pressure in the outlet path. The fluid pressure control assembly is configured to control the throttle mechanism as a function of displacement of the mechanical pressure transducer.

Abstract: A refrigeration unit and a method for controlling same during start-stop operation is provided. The refrigeration unit may include an engine operable between at least a low engine speed and a high engine speed, a compressor operatively coupled to the engine, and a controller operatively coupled to each of the engine and the compressor. The controller may be configured to operate the engine at a reduced low speed during a delay period, extend the delay period based on the reduced low speed, increase a displacement capacity of the compressor based on the extended delay period, and operate the engine at a reduced high speed.

Abstract: A hydraulic drive system for a working machine provides improved safety during forced regeneration. Upon input of a forced regeneration command signal from a forced regeneration switch, a controller detects non-operated states of all hydraulic actuators such as an arm cylinder arranged on a hydraulic excavator based on a lock detection signal from a gate lock detection switch, and also an attitude of a front working mechanism. The attitude is proper from the standpoint of safety. The detection is based on an arm angle signal from an arm angle sensor, a bucket angle signal from a bucket angle sensor and a boom pressure signal from a boom pressure sensor. Taking the detection of the non-operated states and proper attitude as conditions, the controller outputs control signals to a boosting proportional solenoid valve and flow-rate controlling, proportional solenoid valve to make a forced regenerator conduct forced regeneration.

Abstract: A hydraulic controller having at least one input for a hydraulic fluid for controlling the speed of a hydraulic pump driven by an internal combustion engine is characterized in that the controller has at least two inputs, that at least two pressure chambers each connected to one of the inputs are provided, that each of the same has a piston displaceable under pressure from a rest position against the force of a spring into a switched position and that the piston rod thereof engages at the end of a rod or a pull in the switched position.

Abstract: The present a hydraulic system and a method for operating a hydraulic system that includes an engine, at least one hydraulic pump, a pump box interposed between the engine and the at least one hydraulic pump, at least one hydraulic clutch pack interposed between the pump box and the at least one hydraulic pump, at least one valve, a hydraulic fluid reservoir, a clutch actuation pump, and one or more electronics. The at least one hydraulic clutch pack selectively transmits torque to the at least one hydraulic pump. The at least one valve may be opened to supply pressurized hydraulic fluid to the at least one clutch pack and may be closed to interrupt a supply of pressurized hydraulic fluid to the at least one clutch pack in order to selectively engage or disengage the clutch pack.

Abstract: The present disclosure provides a power control apparatus of a construction machine, including: an engine connected to a hydraulic pump to drive the hydraulic pump; and a controller for calculating an engine load ratio defined as a ratio of a load torque of the engine for an engine maximum torque calculated from an input engine target RPM, and calculating an engine RPM command value according to the engine load ratio such that the engine is driven at the target RPM to output the calculated engine load ratio and engine RPM command value to the engine.

Abstract: A hydraulic drive system for a hydraulic working machine sets a delivery pressure at a preset value upon raising a temperature of exhaust gas to a temperature needed for combustion of particulate matter by increasing a load to be applied to an engine. In a non-operation state, a variable restrictor is controlled by a controller and a delivery pressure control valve to increase a delivery pressure of a variable displacement hydraulic pump, so that the load is increased to raise the temperature of exhaust gas to the temperature needed for the particulate matter combustion. At this time, the controller controls the delivery pressure control valve such that a delivery pressure to be detected by a delivery pressure sensor will conform with a preset reference delivery pressure. The reference delivery pressure is set to a minimum pressure that can provide the exhaust gas with combustion heat.

Abstract: An oil-gas vapor collection, storage, and recovery system ensures that no air or oxygen leakage into the production tank occurs when gauging and/or emptying a tank. The system provides a constant reservoir-type storage system by utilizing a variable volume gas bag, expanding with a surge of gas from the separator and with minimal water column pressure from the plunger lift system, thereby containing the gas surge, but contracting with gas dissipation thus minimizing the compressor cycling, while accommodating rapid liquid and vapor influxes into the tank thus maintaining constant tank pressure. With expansion, the bag actuates a switch which activates a compressor, which, in turn, compresses the contained gas into the pipeline. Upon bag collapse, a switch is activated to turn off the compressor. Thus, the system provides constant storage tank pressure because the gas bag accommodates and controls variable gas volume.

Abstract: A system for controlling the pressure output of an engine-driven centrifugal fire pump includes a discharge pressure sensor mounted in the discharge line of the pump. A governor varies the rpms of the engine in response to pressure changes detected by the discharge pressure sensor. If the pressure in the system is higher than the desired output pressure when the engine is running at its idle speed an electronically controlled hydraulic relief valve responsive to the discharge pressure sensor operates to relieve the excess pressure in over pressure situations. If the pressure in the system is lower than the desired output pressure when the relief valve is fully closed, the engine speed is increased.

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: An idle down controller for pressure washers is responsive to the drop in pressure at the pump outlet. The controller includes a sensor disposed in the pump outlet manifold. When the fluid is being bypassed, the manifold pressure drop is communicated to an actuator. The actuator overrides the engine governor and forces the engine throttle to the idle speed. When an operator is discharging a pressurized fluid, the actuator allows the governor to operate the engine at its normal speed.

Abstract: A pressure washer system includes an engine, a water pump, a sprayer, an unloader, and a link. The engine has a throttle system designed to control the speed of the engine. The water pump includes an inlet, a pumping mechanism, and an outlet. The pumping mechanism is designed to be driven by the engine. The sprayer is attached to the outlet of the water pump. The unloader is designed to direct water toward the inlet of the water pump when the unloader is in a first configuration, and to direct water toward the sprayer when the unloader is in a second configuration. Water pressure generated when the sprayer is not actuated moves the unloader to the first configuration. The link connects the unloader and the throttle system of the engine, where the link is designed to adjust the throttle system to a first engine speed when the unloader is in the first configuration, and to adjust the throttle system to a second engine speed when the unloader is in the second configuration.

Abstract: A pressure washer is provided. The pressure washer can include a frame and a power source coupled to the frame. The power source can include an output shaft. The pressure washer can include a centrifugal clutch. The centrifugal clutch can include an input portion operably coupled to the output shaft and an output portion. The input portion of the centrifugal clutch can be operable to be selectively coupled to the output portion. The pressure washer can include a pump assembly, which can include a pump mechanism operably coupled with the output portion of the centrifugal clutch to pressurize a fluid when the input portion of the centrifugal clutch is coupled to the output portion. The pressure washer can also include an actuator in communication with at least the power source to actuate the power source to drive the output shaft.

Abstract: A concrete placement vehicle. The concrete placement vehicle includes a concrete mixing and placement system, at least one vehicle sensor configured to monitor a characteristic of the concrete placement vehicle and at least one concrete system sensor configured to monitor a characteristic of the system for mixing and placing concrete. The vehicle further includes a control system configured to control the operation of the concrete placement vehicle and the concrete mixing and placement system based on inputs received from the at least one vehicle sensor and the at least one concrete system sensor.

Abstract: In an engine drive washing machine, a discharge switch 10 is provided in a jet gun 5. When the switch 10 is turned off, an engine 1 is stopped. When the switch 10 is turned on, the engine 1 is started up to drive a pump 2. When an outlet pressure of the pump 2 is not lower than a predetermined value, a water-discharge valve in the gun 5 is opened to cause the water to be discharged. When the switch 10 is not turned off for a long time, the engine 1 is stopped. When an operator takes up the gun 5 to start the operation, the engine 1 is started up. The engine-drive type of washing machine is provided with a battery 13 for a starter motor, and the battery 13 is charged by a generator function of a starter-motor generator 3 during the operation of the engine 1.

Abstract: The present embodiments relate to a digital over speed circuit including a controller configured to calculate the speed of an engine and shut down the engine electronically when an over speed condition exists. The digital over speed circuit may be easily installed by the end user. Only a single wire is needed between the digital over speed circuit and the engine. Further, the digital over speed circuit does not require a reset or any user action of any kind after the over speed condition has been detected and power removed from the engine. In other words, there is no ON switch, and the user may immediately start the engine again after the engine has stopped and the digital over speed circuit has reset.

Abstract: A system for automatically controlling a pumping unit used in fire suppression comprises a pumping unit, a water flow sensor and a pump controller. The pumping unit has a pump with a suction inlet configured to receive water from an upstream pumping unit and an engine to run the pump. The water flow sensor senses water flow into the suction inlet of the pumping unit. The pump controller receives a water flow sensor signal from the water flow sensor and controls an on/off state of the engine based on the water flow sensor signal.

Abstract: A concrete placement vehicle. The concrete placement vehicle includes a concrete mixing and placement system, at least one vehicle sensor configured to monitor a characteristic of the concrete placement vehicle and at least one concrete system sensor configured to monitor a characteristic of the system for mixing and placing concrete. The vehicle further includes a control system configured to control the operation of the concrete placement vehicle and the concrete mixing and placement system based on inputs received from the at least one vehicle sensor and the at least one concrete system sensor.

Abstract: A hybrid internal combustion engine and air motor system is provided and includes at least one chamber having a drivable member and at least one intake valve and at least one exhaust valve, and a reservoir connected to the chamber through at least one of the intake valve and the exhaust valve. The system further comprises a computer configured to calculate air compressor efficiency during an air compressor mode of operation and select an intake and exhaust valve opening and closing timing sequence for maximizing air compressor efficiency and/or a computer configured to calculate air motor efficiency during an air motor mode of operation and select an intake and exhaust valve opening and closing timing sequence for maximizing air motor efficiency.

Abstract: A rotation control system of a hoist pump includes: the hoist pump (3); an engine (2) for driving the hoist pump (3); a working equipment driven by a hydraulic cylinder that is extendable by hydraulic oil delivered through the hoist pump (3); a hydraulic oil tank that stores the hydraulic oil supplied to the hoist pump (3) and receives the hydraulic oil returned from the hydraulic cylinder; and a controller (9) that controls a rotation speed of the hoist pump (3) to be an allowable rotation speed that is set in advance for preventing cavitation while the hydraulic cylinder is operated.

Abstract: A control system and method for obtaining power on demand from a diesel engine in order to operate vehicle functions and accessories. The method comprised of: (1) determining a flow rate necessary to operate each of a plurality of function hydraulic pumps and an vehicle drive pump associated with the engine; (2) comparing the flow rates of the various hydraulic pumps to determine the greatest flow rate; (3) establishing an engine speed necessary to deliver the greatest flow rate; (4) comparing the engine speed necessary to deliver the greatest flow rate with a current engine speed; and (5) adjusting the current engine speed to provide the greatest flow rate required.

Abstract: A pressure washer includes a water pump and a pressure-sensitive member attached to the water pump. The pressure washer also includes a wire having a first end attached to the pressure-sensitive member. The pressure-sensitive member relays a change in water pressure within the pump through the wire. Additionally the pressure washer includes an engine having a governor spring attached to the wire. Movement of the wire changes a tension of the governor spring. The engine also has a throttle plate attached to the governor spring. The governor spring biases the throttle plate.

Abstract: A rotational speed pickup 71 (traveling speed detection means), a hydraulic pressure sensor 72 (traveling operation detection means), a hydraulic pressure sensor 73 (drive status detection means), and a voltage sensor 74 (transmission shift position detection means) detect parameters regarding the traveling state of a hydraulic traveling vehicle. A control unit 80, a solenoid proportional valve 81, an engine control system 82, and a motor regulator 33 determine the operating state of the hydraulic traveling vehicle based on the parameters regarding the traveling state, and control the equivalent displacement of the traveling system including a hydraulic traveling motor 14 and the maximum flow rate supplied to the hydraulic traveling motor 14 according to the result of determination. The pump flow rate and motor displacement are controlled according to the traveling state in this way, thereby ensuring favorable traveling performance without degrading the fuel efficiency.

Abstract: A method for controlling a hydraulic system includes receiving an operator command signal via an operator command input device; receiving a throttle position signal from a throttle; retrieving from a memory a first predetermined correlation between the operator command signal and a corresponding command flow rate; retrieving from the memory a second predetermined correlation between the throttle position signal and a corresponding available flow rate from a hydraulic pump; determining the command flow rate based on the first predetermined correlation and the operator command signal; determining the available flow rate based on the second predetermined correlation and the throttle position signal; and providing a control signal based on the available flow rate and the command flow rate.

Abstract: A method and system for operating a pump driven by an engine are disclosed, including adjusting and measuring a speed of the engine with a controller electrically coupled to the engine, the controller having encoded therein a computer-readable method of controlling a pump; receiving a first discharge pressure at a first engine speed from a discharge pressure sensor coupled to a discharge line of the pump, and a second discharge pressure at a second engine speed from the discharge pressure sensor; determining a pump constant and an intake pressure in response to the first and second engine speeds; determining a maximum engine speed in response to the pump constant, the intake pressure, and a desired discharge pressure; and, limiting the engine speed to the maximum engine speed.

Abstract: A method of reducing the load of at least one engine arranged in an hydraulic excavator during a speed overload situation of a respective engine, includes reducing a delivery quantity of at least one hydraulic secondary consumer until the respective engine has been returned to a desired operational speed range.

Abstract: A control apparatus of a construction machine includes a hydraulic pump driven by a prime mover, a hydraulic actuator, and a rotation speed detection device for detecting an actual rotation speed of the prime mover. The control apparatus includes a prime mover control device for controlling a rotation speed of the prime mover, and an input torque control device for adjusting an input torque for the hydraulic pump based on a deviation between the actual rotation speed detected by the rotation speed detection device and a control rotation speed set through an operation of the operating device, and the input torque control device executes control to decrease the input torque if the control rotation speed is greater than the actual rotation speed and the deviation calculated by subtracting the control rotation speed from the actual rotation speed is smaller than a predetermined negative value.