1. Technical characteristics of the main components of the hydraulic system
The tractor hydraulic system is composed of an oil pump, control valve, oil cylinder, safety valve, and oil tank.
(1) Working process: When the clutch handle of the oil pump is placed in the "close" position, the oil pump works.
(2) Safety valve. The safety valve is installed on the side of the oil pump and an oil channel in parallel with the main oil channel, which is used to limit the maximum working pressure of the hydraulic system to protect the parts from damage.
(3) Operate the valve. The control valve is a rotary valve type direction control valve, which is used to control the flow direction of the oil, it has three positions of lifting, neutral and falling, which can make the farm tools to achieve lifting, maintaining at a certain height and falling three working conditions. The control valve is installed in a seat hole on one side of the pump body. The spool has a special cross-section shape, forming two arc grooves and two flanges, and the spool is also drilled with a radial hole and an axial hole.
(4) Oil cylinder. The hydraulic cylinder is installed in the oil tank and is composed of a cylinder block, a piston, a piston rod, an oil drain valve and a limit plate. Two O-shaped oil-resistant rubber seals are installed in the annular groove of the piston to seal the matching gap between the cylinder and the piston. One end of the piston rod is connected to the piston by a short pin, and the other end is connected to the inner lifting arm by a pin. The oil inlet hole of the cylinder and the oil outlet of the control valve are connected by tubing. The cylinder piston is equipped with an oil drain valve, its main function is to limit the maximum lifting height of the farm tools, to prevent the piston from extending too much from the cylinder block, resulting in the inner lifting arm to break the fuel tank. Under the action of the spring, the oil drain valve and the oil drain hole on the piston are sealed with "belt coordination" to prevent the leakage of hydraulic oil in the cylinder. When the hydraulic oil from the plunger pump enters the cylinder, push the piston backward. Through the piston rod to promote the inner lifting arm rotation, drive the suspension mechanism to raise the farm tools. When the back end of the drain valve hits the stop plate, the drain valve spring is compressed. There is a gap between the belt matching the oil drain valve and the oil drain hole, the hydraulic oil flows back to the tank through the gap, the piston stops moving, and the farm tool rises to the highest position.
(5) Fuel tank. The fuel tank is composed of a rear cover, a rear cover bottom plate, and a fuel vent plug. It is fixed above the rear of the gearbox housing, replacing the rear axle upper cover. The upper part of the oil tank is equipped with a refueling vent plug, which makes the tank always communicate with the atmosphere and ensures that the pressure above the liquid level is always equal to the atmospheric pressure, so as not to change the pressure in the tank when the oil temperature changes, affecting the oil supply. Unscrew the fuel vent plug to fill the oil tank with hydraulic oil.
(6) Locking device. When the tractor is mounted on the farm tools for long distances, the farm tools need to be raised to the highest position. In order to reduce the power consumption of the engine and the wear of the plunger oil pump, the plunger oil pump can be separated at this time to stop the oil pump. To prevent the farm tools from falling under the action of self-weight during driving, a locking device is installed in the lower back of the fuel tank. When the control handle is pulled forward to the vertical position, the inner lifting arm is in a mechanical locking state, which can make the suspended farm tools reliably fixed in the highest position to ensure the safe running of the unit.
2. Hydraulic system use and maintenance points
(1) During the maintenance of each shift, the reliability of the oil tank level and the hydraulic system seal should be checked, and there should be no oil leakage parts. The hydraulic pump, control valve and hydraulic cylinder, and other precision parts, have been adjusted before the factory, generally do not adjust in use, must be adjusted, should be carried out by professionals in the repair shop on the test bench. In use, the opening pressure of the safety valve of the hydraulic system can not be adjusted at will, so as not to cause the gear oil pump, the distributor, the multi-way reversing valve housing and the oil pipe and other parts to burst.
(2) When replacing hydraulic oil, pay attention to the following matters: First, the engine is turned off, and the oil in the oil tank and hydraulic system parts is released while it is hot. The second is to add the cleaning diesel fuel to the hydraulic system tank, start the engine, and lift the hydraulic system 4 to 5 times with the suspension mechanism (so that the hydraulic system works reciprocately). The third is to turn off the engine and release the cleaned diesel oil from the fuel tank, distributor, and cylinder respectively. Fourth, take out the filter in the hydraulic tank and clean it with diesel oil.
(3) In the hydraulic system, the oil channel inlet, outlet, and positioning pin hole are equipped with O-type sealing rings, pay attention to not losing when disassembling, such as the sealing ring should be replaced.
