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.

A construction machine that precisely enables derivation of the operation characteristics of hydraulic actuators in a high-velocity area with less calibration operation is provided. A controller (10) has a calibration mode in which the controller (10) derives operation characteristics (α(xs)) representing a relation among a spool position (xs) of a meter-in valve (8a1), an operation velocity (Va) of a hydraulic actuator (4a), and a differential pressure (ΔP) across the meter-in valve (8a1), and is configured to, in a case where the spool position (xs) of the meter-in valve (8a1) has changed in a direction to increase the opening area of the meter-in valve (8a1) in the calibration mode, output a command signal to increase the opening area of a bleed-off valve (8b1) to a bleed-off solenoid proportional pressure-reducing valve (8b2) as a command signal to reduce the differential pressure (ΔP).

A refuse vehicle includes a chassis, an energy storage device, a vehicle body, an electric power take-off system, and a hydraulic component. The energy storage device is supported by the chassis and is configured to provide electrical power to a prime mover. Activation of the prime mover selectively drives the refuse vehicle. The vehicle body is supported by the chassis, and includes an on-board receptacle for storing refuse therein. The electric power take-off system is positioned on the vehicle body, and includes an electric motor configured to drive a hydraulic pump to convert electrical power received from the energy storage device into hydraulic power. An amount of electrical power at least one of received by and provided to the electric motor is limited by a controller to control an output characteristic of the hydraulic pump. The hydraulic component is in fluid communication with the hydraulic pump and configured to operate using hydraulic power from the electric power take-off system.

A hydraulic system includes: a cylinder that moves a moving object in a vertical direction by extension and retraction of a rod; a first bidirectional pump connected to a head-side chamber of the cylinder by a first supply/discharge line; a second bidirectional pump connected to a rod-side chamber of the cylinder by a second supply/discharge line and coupled to the first bidirectional pump in a manner enabling torque to be transmitted between the first and second bidirectional pumps; a relay line connecting the first and second bidirectional pumps such that a hydraulic liquid discharged from one of the first and second bidirectional pumps is introduced into the other of the first and second bidirectional pumps; and a servomotor that drives the first or second bidirectional pump. At least one of the first and second bidirectional pumps is a variable displacement pump whose delivery capacity per rotation is freely variable.

A shovel includes an undercarriage, an upper slewing structure which is rotatably mounted on the undercarriage, a boom attached to the upper slewing structure, an arm attached to a tip end of the boom, an auxiliary attachment attached to a tip end of the arm, a main pump configured to supply a hydraulic oil to the auxiliary attachment and other hydraulic actuators, and a controller. The controller performs a setting related to a flow rate of the main pump at a time of a combined operation in which the auxiliary attachment and the other hydraulic actuators are operated simultaneously.

An open center hydraulic system (100) includes a tank configured to hold hydraulic fluid, a pump configured to provide pressurized hydraulic fluid from the tank, and a shunt valve configured to adapt a first opening area between a first input port and a first output port of the shunt valve dependent on a first control signal. The first input port is coupled to the pump, and the first output port is coupled to the tank. A first actuator valve is coupled to the first input port and configured to adapt a second opening area of the first actuator valve dependent on a second control signal. A hydraulic valve control unit is configured to determine a first opening area value and a second opening area value based on user input data and a predetermined relation dependent on the user input data, sending the first control signal, indicative of the first opening area value and sending the second control signal indicative of the second opening area value.

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.

An over-pressure protection system includes a main body housing defining a main body chamber configured to receive a fluid therein, wherein the main body housing comprises a spring, the main body housing configurable in a collapsed configuration and an expanded configuration; and a pressure sensor configured to measure a fluid pressure of the fluid, the pressure sensor configurable in an activated mode and a deactivated mode; wherein, in the collapsed configuration, the spring biases main body housing inward at an intermediate point of the main body housing such that the main body housing defines a substantially hourglass shape.

Provided is a work vehicle which can prevent an engine from stalling regardless of type of a system mounted on a vehicle body. In a wheel loader 1 equipped with a loading work device 11 operated by an electric operation lever 19, first and second directional control valves 5, 6 include neutral positions 5N, 6N for causing hydraulic oil discharged from a hydraulic pump 12 to return to a hydraulic oil tank 10, respectively, and in the case where a discharge pressure P of the hydraulic pump 12 is a main relief pressure Pr or more and an engine rotational speed N is less than a low idle rotational speed NL, a controller 2, 2A restricts the output of control signals to first and second solenoid control valves 3, 4 so as to cause the first and second directional control valves 5, 6 to be switched to the neutral positions 5N, 6N, respectively.

An electrohydraulic control device for an adjustable hydraulic pump system includes a valve device, an electronic control unit and a first fluid sensor. The valve device includes a pressure inlet, a tank outlet and a first electromagnetically actuated valve. An outlet pressure of the first adjustable hydraulic pump system is applied to the pressure inlet. The first fluid sensor detects an actual value of a fluid parameter of the first adjustable hydraulic pump system and transmits it to the electronic control unit. The electronic control unit includes computer-based modeling of the dynamics of the first adjustable hydraulic pump system, and actuates the first electromagnetically actuated valve based on the actual value of the fluid parameter and the computer-based modeling.