1. The output flow of the hydraulic pump is insufficient or does not output oil

(1) Insufficient amount. The reason is that the resistance on the suction line is too large or the oil supplement is insufficient. If the speed of the pump is too high, the liquid level in the oil tank is too low, the oil inlet pipe is leaking, and the oil filter is blocked.

(2) The leakage is too large. The gap of the pump is too large, caused by poor sealing. The oil pan is scratched with metal fragments, iron, and other end surface oil; the surface of the sealing one-way valve mechanism is in or out, the bearing surface of the pump body and the oil pan trachoma study marks and other variables. By checking the foreign matter mixed in the hydraulic oil of the pump body, the damaged part of the pump can be determined.

(3) The tilt angle of the swashplate is too small, and the displacement of the pump is small. This requires adjusting the variable piston and increasing the tilt angle of the swashplate.

2. The oil discharge is not zero at the neutral position

When the inclination angle of the American PARKER variable plunger pump is zero, it is called the neutral position, and the output flow of the pump should be zero at this time. But sometimes the middle position deviates from the middle point of the adjustment mechanism, and the middle point still has flow output. The reason for this is to deviate from the controller, lose or damaged position, it must be re-zeroed and tightened or replaced. This phenomenon can also occur if the angle retention of the pump is insufficient and the bevel trunnion is worn.

3. The output flow fluctuates

The output flow fluctuation is related to many factors. The variable pump can be considered to be caused by poor control of the variable mechanism, such as foreign matter entering the variable mechanism, scratching the plug on the control piston, marking steps, wear marks, etc., resulting in unstable motion of the control piston. Due to the lack of energy amplifiers or damaged components, which are characterized by differences in the performance of the control springs between the damper pistons, the movement of the control pistons will cause instability. Unstable flow is often accompanied by pressure fluctuations. Such failures generally require disassembling the hydraulic pump, replacing damaged parts, increasing damping, increasing spring stiffness, and control pressure.

4. Abnormal output pressure

The pump output pressure is determined by the load, which is roughly proportional to the input torque. There are two types of faults for abnormal output pressure.

(1) The output pressure is too low

When the pump is in the self-priming state, if there is air leakage in the oil inlet pipe or large leakage in the hydraulic cylinder, one-way valve, reversing valve, etc., the pressure will not rise. This requires finding out where the air is leaking, tightening, and replacing the seals to increase the pressure. If the fail-safe valve or adjustment pressure is low, the system pressure cannot rise, adjust the pressure relief valve or repair it. If the cylinder body and the valve plate quoted by the agricultural special motor have a large amount of leakage, and the cylinder body may be broken in severe cases, the mating surface should be reground or the hydraulic pump should be replaced.

(2) The output pressure is too high

If the circuit load continues to rise, the pump pressure also continues to rise, which is normal. If the load is constant, and the pressure of the pump exceeds the pressure required by the load, you should check the hydraulic components other than the pump, such as directional valves, pressure cabinets, transmission devices, and oil return pipelines. If the pressure is too high, the relief valve should be adjusted.