Systems and methods for calibration of an electrohydraulic control valve are provided. In one aspect, a method for calibrating an electrohydraulic control valve includes providing fluid communication between the pump and the reservoir through a bypass calibration orifice. The bypass calibration orifice defines a known restriction. The method further includes measuring a pressure drop across the bypass calibration orifice, commanding the electrohydraulic control valve, calculating a pressure drop across the electrohydraulic control valve, recording the command applied to the electrohydraulic control valve corresponding with the calculated pressure drop across the electrohydraulic control valve, and calibrating the electrohydraulic control valve based on at least two of the recorded command, the known restriction, the measured pressure drop across the bypass calibration orifice, and the calculated pressure drop across the electrohydraulic control valve.

A rotating head assembly includes a body, an implement, a clamp assembly, a drive member, a hydraulic motor, and a bypass circuit. The drive member is threadingly connected to a first clamp member and a second clamp member. The hydraulic motor is connected to the drive member to cause the drive member to rotate in a selected direction. An inlet of the bypass circuit is in fluid communication with an inlet of the hydraulic motor to receive a portion of the pressurized hydraulic fluid passing to the hydraulic motor. An outlet of the bypass circuit is in fluid communication with the outlet of the hydraulic motor. At least one bypass valve is interposed between the inlet of the bypass circuit and the outlet of the bypass circuit. The bypass valve has an actuator positioned adjacent one of the first clamp member and the second clamp.

A hydraulic system includes a first hydraulic device to be operated by an operation fluid, a second hydraulic device, the second hydraulic device being configured to be operated by the operation fluid, a first control valve to control the first hydraulic device, a second control valve disposed on a downstream side of the first control valve and configured to control the second hydraulic device, a communication tube connecting the first hydraulic device to the first control valve, the communication tube being configured to supply a return fluid that returns from the first hydraulic device to the first control valve, a supply fluid tube connecting the first control valve to the second control valve and being configured to supply the return fluid to the second control valve, and a connection fluid tube disposed on the first control valve, the connection fluid tube connecting the communication tube to the supply fluid tube.

A shovel includes a lower traveling structure, an upper swing structure swingably mounted on the lower traveling structure, an engine mounted on the upper swing structure, a hydraulic pump configured to be driven by the engine, and processing circuitry configured to determine a command value by energy saving control and to control a flow rate of hydraulic oil discharged by the hydraulic pump according to the command value. The processing circuitry is configured to control the command value.

An object of the present invention is to provide a construction machine that allows easy and accurate calibration of a pressure sensor and enables accurate control of hydraulic actuators. A controller increases the delivery pressure of a hydraulic pump in a state in which first and second meter-out valves and a second meter-in valve are closed and in which a first meter-in valve is opened, and calibrates a first pressure-calculation map such that a pressure calculated on the basis of the first pressure-calculation map matches a pressure calculated on the basis of a supply-pressure-calculation map, and increases the delivery pressure of the hydraulic pump in a state in which the first and second meter-out valves and the first meter-in valve are closed and in which the second meter-in valve is opened, and calibrates a second pressure-calculation map such that a pressure calculated on the basis of the second pressure-calculation map matches the pressure calculated on the basis of the supply-pressure-calculation map.

A hydraulic system including a first cylinder conduit configured to couple to a cylinder, an auxiliary conduit configured to couple to a case drain conduit, and a pressure regulator coupled to the first cylinder conduit and to the auxiliary conduit. The pressure regulator may block fluid flow to the auxiliary conduit if a first fluid pressure is less than or equal to a threshold pressure and enable fluid flow if the first fluid pressure is greater than the threshold pressure. The hydraulic system further includes a supplemental conduit with a check valve that directs fluid from the auxiliary conduit to a reservoir. The check valve blocks fluid flow if a second fluid pressure is less than or equal to a third fluid pressure, and enables fluid flow if the second fluid pressure greater than the third fluid pressure.

Provided is a hydraulic circuit, for a construction machine, which drives an actuator by merging pressure oil from a fixed-volume pump into a center bypass oil path from a variable-volume pump to an oil tank, wherein the flow rate of flow from the fixed-volume pump to the center bypass oil path can be controlled in accordance with a requested flow rate of the actuator. A distribution direction-switching valve, which has a first oil path from a fixed-volume pump to an oil tank and a second oil path from the fixed-volume pump to a first center bypass oil path, has a first signal reception unit which causes a spool to slide in a direction in which the first oil path is formed, and a second signal reception unit which causes a spool to slide in a direction in which the second oil path is formed, and determines a distribution ratio of pressure oil flowing to the first oil path and the second oil path in accordance with the difference in size of the signals received by the first signal reception unit and the second signal reception unit, the first signal reception unit receiving a signal based on a negative control signal.

Sod harvesters can have hydraulic systems that are configured to actuate components with precise timing. The hydraulic system of a sod harvester can be configured to maintain the temperature of hydraulic fluid both during harvesting and while harvesting is paused to thereby eliminate or minimize the occurrence of periods of variation in the timing of actuation of the components that the hydraulic fluid drives. As a result, these components can be consistently actuated with precise timing even after harvesting has been paused. Additionally, such configurations can minimize the amount of time required to warm the hydraulic fluid to a steady operational temperature.

Provided is a work machine which can achieve both of excellent operability when an operator manually operates a machine body or a work device and an accuracy of control of the machine body or the work device when a controller performs automatic control. The controller is configured to, in a case where the automatic control function selector switch gives an instruction to disable the automatic control function, adjust an opening amount of a bleed-off valve to a maximum opening amount or an opening amount corresponding to input amounts of control levers, and in a case where the automatic control function selector switch gives the instruction to enable the automatic control function, adjust the opening amount of the bleed-off valve, in at least part of an operation region of the control levers, so as to be smaller than the opening amount with the instruction to disable the automatic control function being given.

A shovel includes a lower traveling structure, an upper swing structure mounted on the lower traveling structure, an engine mounted on the upper swing structure, a hydraulic pump configured to be driven by the engine, a hydraulic actuator, an operating device configured to operate the hydraulic actuator, and a hardware processor configured to control the discharge quantity of the hydraulic pump through negative control and change a control characteristic of the negative control according to the details of an operation on the operating device.