The hydraulic system of the domestic PY180 grader is all included, which includes the hydraulic circuit of the working device, the steering hydraulic circuit and the control hydraulic circuit.

Working device hydraulic circuit

PY180 grader working device hydraulic circuit consists of high pressure double gear pump 13, manual control valve 19 and 20, single and double oil circuit switching valve 18, charge valve 25, pressure limiting valve 16, two-way hydraulic lock 26, one-way throttling The valve 27, the scraper right and left lift cylinders 7 and 8, the scraper swing cylinder 6, the scraper take-up cylinder 5, the shovel shift cylinder 3, the ripper lift cylinder 10, the scraper slewing motor 2, and the like. The pump II in the double pump can supply the pressure oil to the blade lift cylinder 1, the scraper rotary motor 2, the front wheel tilt cylinder 11, the scraper swing cylinder and the scraper right lift cylinder through the multi-way control valve 20; The brake one way provides pressure oil. When the oil pressure of the two accumulators 31 reaches 15 MPa, the restriction valve will automatically interrupt the oil circuit of the brake system, and at the same time, the oil circuit connecting the multi-way control valve 19 is turned on, and the oil cylinders and scrapers are respectively lifted to the ripper. The angle change cylinder, the articulated steering cylinder, the scraper extraction cylinder and the scraper left lift cylinder provide pressurized oil.


When the dual pumps I and II supply oil to two separate working device hydraulic circuits, the flow rates of the two hydraulic circuits are the same. When the multi-way control valves of the two circuits are in the "neutral position", the oil of the two circuits will flow back to the pressure tank through the overflow valve and the oil filter. At this time, the working devices in the multi-way control valve are changed. The normal port of the valve is connected to the oil tank, and the corresponding hydraulic cylinder and hydraulic motor of the working device are in a hydraulic lock state.

The hydraulic cylinder and hydraulic motor of the PY180 grader working device are double-acting. When one or several manual reversing valves are operated into the left or right position, the pressure oil will enter the corresponding hydraulic cylinder working chamber, related The working device starts to operate according to the predetermined requirements; all the reversing valves in the "neutral" position are locked, and the corresponding working device hydraulic cylinder or hydraulic motor is in the hydraulic locking state. When any hydraulic cylinder or hydraulic motor enters the left or right position, the flow control valve in the hydraulic circuit (the pump I or the pump II working circuit) is provided with a flow control valve to enable the hydraulic cylinder or The movement speed of the hydraulic motor remains basically stable to improve the smoothness of the movement of the grader working device.

When the hydraulic system is overloaded, the above double circuit can be opened and unloaded through the safety valve provided in the oil passage reversing valve to ensure the safety of the system (system safety pressure 13MPa). Since the power consumed by the scraper motor and the blade lift cylinder is large, a safety valve for the scraper and the blade lift oil passage is added to the pump II hydraulic circuit to ensure the safety pressure of the hydraulic system is 18 MPa.


When the oil path reversing valve is in the position shown, the double circuits formed by the pump I and the pump II can work independently, and the working device of the leveling machine can change and adjust the working position by manipulating the corresponding manual reversing valve. When adjusting the lifting position of the scraper, it should work simultaneously with the double circuit to ensure the synchronous movement of the left and right lifting cylinders of the scraper to improve work efficiency. In order to increase the moving speed of the working device, the oil circuit switching valve can be placed in the left position, and the two circuits of the pump I and the pump II can be combined into one circuit (combination circuit), the flow rate is doubled, and the moving speed of the working device is correspondingly Double the doubling, shortening the auxiliary time during the work of the grader, and improving the productivity of the grader.

A bidirectional hydraulic lock 26 is arranged on the left and right lift cylinders of the scraper to prevent the rear end suspension weight of the traction frame and the ground reaction force impact force from causing displacement of the lock cylinder. In order to achieve a smooth descent of the dozer blade and a smooth swing of the scraper left and right, a one-way throttle valve is provided in the lower chamber of the dozer lift cylinder (with the rod cavity) and the upper and lower chambers of the scraper cylinder to control the return flow rate of the oil. Make sure that the dozer blade and scraper move without inertial impact. The two-chamber of the front wheel tilting cylinder is provided with a throttle valve, and the reversing valve for ensuring the tilting of the front wheel is further provided with two one-way replenishing valves, and the oil supply from the pressure tank can be supplemented by the valve when the tilting cylinder is insufficiently supplied with oil. In order to prevent the front wheel from shaking due to cavitation, it ensures the safety of the grader when driving and steering. In order to meet the requirements of the hinged steering cylinder and the front and rear frame positioning of the left and right hinged steering cylinders 9, an oil filling valve 25 is provided on the oil returning path of the hinged steering reversing control valve, and the oil can be directly supplied from the pressure oil tank when the system is insufficiently supplied with oil. In order to achieve a stable articulated steering and reliable positioning of the grader.


In the parallel hydraulic circuit of various working devices on the grader, since both ends of the left and right lift cylinders of the scraper are equipped with hydraulic locks, the oil in the oil inlet chamber of the scraper lift cylinder cannot be reversed when the cylinder piston reaches the limit position. Return to the fuel tank. The other working device cylinders and the scraper rotary motors are not provided with bidirectional hydraulic locks. In order to prevent oil flow backwards when the working cylinders or hydraulic motor inlet chambers and the reversing valves enter the "median position", the ripper and scraper are used in the soil. In the oil path such as angle change, hinged steering, scraper extraction, dozer blade, scraper swing, front wheel tilt and scraper rotation, the inlet port of the negative closed reversing control valve is provided with a check valve.

The PY180 grader adopts a closed pressure oil tank with an exhaust valve on it, which can control the pressure inside the fuel tank to be 0.07MPa, which helps the oil pump and steering oil pump of the working device to absorb oil normally, and can prevent cavitation and oil pollution. Reduce hydraulic system failure and extend the life of hydraulic components.

Steering hydraulic circuit

The hydraulic hydraulic circuit of the PY180 motor grader is composed of main hydraulic components such as the steering pump 14, the emergency steering pump 15, the steering valve 22, the hydraulic steering gear 23, the steering cylinder 4, the cooler 28, the bypass indicating valve 21, and the pressure oil tank 24. . When the grader turns, the pressure oil supplied by the steering pump passes through the flow control valve and the steering valve to enter the hydraulic steering gear at a steady flow rate, and then enters the reverse working chamber of the left and right steering cylinders of the front axle to push the left and right front wheels. The knuckle arm deflects the wheel for steering to the left or right. The safety valve in the steering gear can protect the safety of the steering hydraulic circuit, that is, the safety valve is opened and unloaded when the circuit is overloaded (working pressure exceeds 15 MPa).


When the steering oil pump fails and the pressure oil cannot be supplied, the steering valve automatically turns on the emergency steering pump driven by the output shaft of the transmission, and the pressure oil supplied by the pump can enter the steering circuit to ensure the normal steering movement. When the steering pump or emergency steering pump fails, the bypass indicator valve is turned on and the monitor indicator is displayed to alert the driver. (This article is from SINOMACH)

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