It is an object of the present invention to provide a construction machine having a good engine starting property in a low temperature environment.

The construction machine of the present invention includes: an electric pump having a delivery port connected to a line part of a pilot line, the line part connecting a pilot pump with a pilot control valve; a motor that drives the electric pump; and a temperature sensor that measures a temperature of a hydraulic working fluid delivered from the pilot pump. A controller starts driving of the motor in the case where a key switch is operated from a key OFF state to a key ON state and where the temperature of the hydraulic working fluid measured by the temperature sensor is lower than a predetermined temperature.

Provided is a work machine with which responsiveness of a hydraulic actuator can be improved when driving the hydraulic actuator through an electric lever-type operation device. A controller 100 further includes: an operation direction determining section 116 configured to determine operation directions of operation devices 2a and 2b; and a standby pressure switching command section 117 configured to output a standby pressure switching command to a first target pilot pressure correction section 112 or a second target pilot pressure correction section 113 which corresponds to a solenoid proportional valve that does not correspond to the operation direction from among first solenoid proportional valves 41a, 42a, 42b, 43a, 43b, and 44a and second solenoid proportional valves 41b, 42c, 42d, 43c, 43d, and 44b. The first target pilot pressure correction section and the second target pilot pressure correction section are configured to switch a first standby pressure α to a second standby pressure β set lower than the first standby pressure in a case in which the standby pressure switching command has been inputted.

Provided is a work machine with which responsiveness of a hydraulic actuator can be improved when driving the hydraulic actuator through an electric lever-type operation device. A controller 100 further includes: an operation direction determining section 116 configured to determine operation directions of operation devices 2a and 2b; and a standby pressure switching command section 117 configured to output a standby pressure switching command to a first target pilot pressure correction section 112 or a second target pilot pressure correction section 113 which corresponds to a solenoid proportional valve that does not correspond to the operation direction from among first solenoid proportional valves 41a, 42a, 42b, 43a, 43b, and 44a and second solenoid proportional valves 41b, 42c, 42d, 43c, 43d, and 44b. The first target pilot pressure correction section and the second target pilot pressure correction section are configured to switch a first standby pressure α to a second standby pressure β set lower than the first standby pressure in a case in which the standby pressure switching command has been inputted.

A hydraulic leak detection system includes a leak detection switch responsive to a level of hydraulic fluid in a tank used by a hydraulic mowing circuit and a lift and lower circuit of a grass mowing machine. The system includes a controller that activates a warning indicator if the leak detection switch indicates the level of hydraulic fluid in the tank is low, but allows the hydraulic mowing circuit and the lift and lower circuit to continue operating until the lift and lower circuit reaches a fully raised position. A solenoid valve may control the level of hydraulic fluid in the tank based on temperature of the hydraulic fluid.

A work vehicle includes a lifting mechanism to control at least one of a height and a posture of a work machine connected to the work vehicle. The lifting mechanism is able to control at least one of the height and the posture by using a hydraulic drive. The work vehicle includes an oil-temperature acquirer to acquire an oil temperature to be used for the hydraulic drive, a maximum oil amount setter to set a maximum oil amount according to the oil temperature acquired by the oil-temperature acquirer, the maximum oil amount being a maximum value of a supply amount of oil used to drive the hydraulic drive, and a hydraulic drive controller to control the hydraulic drive below the maximum oil amount set by the maximum oil amount setter.

An actuator assembly includes a cylinder disposed in an actuator housing, the cylinder having a cylinder interior is in fluid communication with a source of pressurized fluid. A ram member has a piston head within the cylinder interior, and pressure on the piston head moves the ram member. An end of the ram member acts on a collar having a collar interior, and an end of a rod member is disposed within the collar interior. The rod member is displaceable relative to the collar such that the end of the rod member does not contact the collar. Accordingly, fluid in the cylinder interior acting on the ram member may expand due to thermal expansion without damaging a hard stop at an opposite end of the rod member and without losing system pressure by triggering a relief valve.

An actuator assembly includes a cylinder disposed in an actuator housing, the cylinder having a cylinder interior is in fluid communication with a source of pressurized fluid. A ram member has a piston head within the cylinder interior, and pressure on the piston head moves the ram member. An end of the ram member acts on a collar having a collar interior, and an end of a rod member is disposed within the collar interior. The rod member is displaceable relative to the collar such that the end of the rod member does not contact the collar. Accordingly, fluid in the cylinder interior acting on the ram member may expand due to thermal expansion without damaging a hard stop at an opposite end of the rod member and without losing system pressure by triggering a relief valve.

Provided are embodiments for a system including an adaptive controller, wherein the system includes a hydraulic actuator including a fluid medium, and a sensor that is disposed on the hydraulic actuator, wherein the sensor is configured to obtain sensor data of the actuator. The system also includes a processor configured to calculate an ultrasonic velocity in the fluid medium using the sensor data, wherein the processor is further configured to determine a temperature of the fluid medium based at least in part on the calculated velocity, and a controller coupled to the actuator, wherein the controller is configured to control the actuator based at least in part on the calculated velocity and determined temperature. Also provided are embodiments for a method for operating the adaptive controller.

Disclosed embodiments include power machines, and hydraulic systems for power machines, in which a machine controller is configured to detect high temperature conditions of the hydraulic oil and to responsively control or reduce the overall torque available from the engine to reduce heat generation in the hydraulic system.

Disclosed embodiments include power machines, and hydraulic systems for power machines, in which a machine controller is configured to detect high temperature conditions of the hydraulic oil and to responsively control or reduce the overall torque available from the engine to reduce heat generation in the hydraulic system.