A circle drive system with clutch protection in motor graders is disclosed. The circle drive system includes a hydraulic motor that is configured to receive a pressurized fluid and generate a torque for a rotation of a circle and a moldboard. The circle drive system also includes a gearbox to transfer the torque generated by the hydraulic motor to the circle. Further, the circle drive system includes a clutch connected to the hydraulic motor at one end and to the gearbox at another end. In addition, the circle drive system also includes a hydraulic circuit having a pressure relief valve to relieve the pressurized fluid supplied to the hydraulic motor when a pressure of the pressurized fluid exceeds a predefined threshold. The pressure relief valve thereby, limits the torque generated by the hydraulic motor to less than or equal to a torque capacity of the clutch.

An electrically powered hydraulic system for a working machine includes: an electric motor to power a working hydraulic pump. A flow of hydraulic fluid generated by the hydraulic pump is controlled by the operation rotational speed of the electric motor. An electronic control unit is configured to: when an operator input device is in a first operating range, maintain the electric motor at a constant rotational speed, and control a variation in flow of hydraulic fluid to the hydraulic function with an electronically controlled control valve, and when the operator input device is in a second operating range, control a variation in flow of hydraulic fluid by varying the electric motor rotational speed and by controlling the control valve, according to displacement of the operator input device.

A construction machine traveling control system is provided. The construction machine traveling control system includes first and second electric traveling pedals for outputting manipulation values including electric signals in response to the driver's manipulation and thereby operating first and second traveling motors connected thereto, respectively; a traveling pattern input means installed in the driving room so as to enable the driver to input a construction machine traveling pattern; a controller electrically connected to the first and second electric traveling pedals and to the traveling pattern input means; and a hydraulic circuit electrically connected to the controller so as to control the flow rate of operation oil supplied to the first and second traveling motors, as well as the flow of the operation oil, according to the command values delivered from the controller.

An object of the present invention is to provide a construction machine that is equipped with a pressure accumulating device, which accumulates the return oil of an actuator, and that is capable of adjusting the operation speed of the actuator according to the revolution speed of a prime mover. For this purpose, in a construction machine including a prime mover, a revolution speed setting device that sets a revolution speed of the prime mover, an actuator, a pressure accumulating device that can supply and discharge a hydraulic fluid to and from the actuator, a first control valve disposed on a hydraulic fluid line that connects the pressure accumulating device and the actuator to each other, an operation device that gives an instruction for operation of the actuator, and a controller that is inputted with an operation signal of the operation device and outputs a control signal to the first control valve, the controller controls the first control valve according to an operation amount of the operation device and the revolution speed set by the revolution speed setting device.

A soil processing machine includes a hydraulic drive system including an electrohydraulic pressurized fluid source with at least one electric motor and at least one hydraulic drive pump, a hydraulic drive circuit fed with pressurized fluid by the at least one hydraulic drive pump, at least one hydraulic drive motor fed with pressurized fluid from the hydraulic drive circuit, and a discharge valve assembly for discharging fluid from the hydraulic drive circuit to a fluid reservoir. The hydraulic drive system is designed to operate the discharge valve assembly as a function of at least one of the following parameters: a temperature of the fluid in the hydraulic drive circuit, an ambient temperature, a viscosity of the fluid in the hydraulic drive circuit, a degree of contamination of the fluid in the hydraulic drive circuit, a period of time since the last start-up of the hydraulic drive system, a period of time since the last fluid was discharged from the hydraulic drive circuit.

In a hydraulic system for a working machine, a controller is configured or programmed to increase an output-port pressure of one activation valve for one hydraulic device and an output-port pressure of another activation valve for another hydraulic device to a normal pressure higher than a preloading pressure from a state where the output-port pressure of the one activation valve is equal to the preloading pressure and the output-port pressure of the other activation valve is lower than the preloading pressure, by causing the output-port pressure of the one activation valve to be lower than the preloading pressure and increasing the output-port pressure of the other activation valve to the normal pressure.

A loading machine for loading, hauling, and dumping material about a worksite includes a lifting implement pivotally joined to a machine frame to articulate with respect to a work surface. A lift sensor is operatively configured to measure vertical articulation of the lifting mechanism. An electronic controller communicating with the lift sensor can be programmed to operate the loading machine in one of a rated performance mode and a limited performance mode depending upon the vertical articulation of the lifting implement with respect to the work surface.

A hydraulic system for operating a circle drive gear of a grading machine includes a pump configured to output pressurized fluid, a directional control valve fluidly coupled to the pump, a bidirectional hydraulic motor located downstream of the directional control valve and fluidly coupled to the directional control valve via hydraulic lines. The hydraulic motor has an output shaft that is configured to be rotationally driven by pressurized fluid output by the pump. Dual counterbalance valves may be disposed within the hydraulic circuit of the directional control valve and hydraulic motor such that any gearbox driven by the hydraulic motor is protected from external opposing forces. Accordingly, motion in the circle drive system is hydraulically locked at the beginning and release of a circle rotation command with the help of fluid pressure in the hydraulic lines.

A hydraulic system controller is disclosed. The hydraulic system controller may determine a maximum active circuit pressure of a set of active hydraulic circuits of the hydraulic system, wherein the hydraulic system includes a hydraulic pump to cause fluid to flow throughout the set of active hydraulic circuits; determine a circuit pressure of a hydraulic circuit of the hydraulic system; determine, based on a hydraulic flow command for the hydraulic circuit and the circuit pressure, a desired circuit delta-pressure for the hydraulic circuit; determine, based on the desired circuit delta-pressure and a pressure difference between the maximum active circuit pressure and the circuit pressure, a circuit valve setting for a circuit valve of the hydraulic circuit; and cause a control device to set a position of the circuit valve according to the circuit valve setting.

A grader and a blade control method wherein the grader includes: a blade mechanism including a blade; a blade adjusting mechanism including a plurality of adjusting means respectively corresponding to at least two degrees of freedom of the blade, and configured to adjust a spatial position and/or angle of the blade; a blade position detecting mechanism configured to detect a slope parameter for characterizing a spatial position of the blade; a motion trajectory library configured to store motion functions of the plurality of adjusting means respectively when different operation conditions and/or different grades are switched; a controller configured to call a corresponding motion function in the motion trajectory library according to a set operation condition and a required slope, and control at least one of the plurality of adjusting means according to a position parameter of the blade and the motion function.