The serious wear of the excavator hydraulic pump has a fatal impact on the excavator. Therefore, such problems of the excavator must be solved in time. When repairing the excavator hydraulic pump, find out the cause of the fault from the following three points:.
(1) Check the internal leakage of the boom cylinder
The simplest way is to raise the boom to see if it has obvious free fall. If the fall is obvious, disassemble the oil cylinder for inspection. If the seal ring is worn, it should be replaced.
(2) Check the control valve
First, clean the safety valve and check whether the valve core is worn. If it is worn, replace it. If there is no change after the installation of the safety valve, check the wear of the control valve core. The service limit of the clearance is generally 0.06mm. If it is seriously worn, replace it.
(3) Measure the pressure of the hydraulic pump
If the pressure is low, adjust it. If the pressure cannot be adjusted, the hydraulic pump is severely worn.
1、 Generally, the main reasons why the boom cannot be lifted with load are:.
1. The excavator hydraulic pump is severely worn
During low-speed operation, the internal leakage of the pump is serious. During high-speed operation, the pressure of the pump is slightly increased. However, due to the wear and internal leakage of the pump, the volumetric efficiency is significantly reduced, and it is difficult to reach the rated pressure. The long-time operation of the hydraulic pump aggravates the wear and the oil temperature rises, resulting in the wear of the hydraulic components and the aging, damage, loss of sealing capacity, deterioration of the hydraulic oil, and finally the failure.
2. Unreasonable selection of hydraulic components
The specification of the boom cylinder is 70 / 40 non-standard series, and the seals are also non-standard parts. The manufacturing cost is high and the replacement of the seals is inconvenient. The small diameter of the boom cylinder is bound to make the system set pressure high.
2、 Improvement and effect.
(1) Improve the design of hydraulic system.
After many times of argumentation, the advanced priority valve and load sensing full hydraulic steering gear are finally adopted. The new system can preferentially distribute the flow to the steering according to the Steering requirements. No matter the load is large or small, the steering wheel speed is high or low, the oil supply is sufficient, and the rest can be supplied to the working device circuit, thus eliminating the loss of success rate caused by excessive oil supply in the steering circuit and improving the system efficiency, It reduces the working pressure of the hydraulic pump and reduces the serious wear of the excavator hydraulic pump.
(2) Optimize the design of boom cylinder and hydraulic pump.
Reduce the working pressure of the system. Through optimization calculation, the boom cylinder adopts standard series 80 / 4, the hydraulic pump displacement is increased from 10ml / R to 14ml / R, and the system set pressure is 14MPa, which meets the lifting force and speed requirements of the boom cylinder.
1. The engine speed decreases.
First, test the output power of the engine itself. If the output power of the engine is lower than the rated power, the fault may be caused by poor fuel quality, low fuel pressure, incorrect valve clearance, a cylinder of the engine does not work, incorrect fuel injection timing, incorrect fuel quantity setting value, air leakage of the intake system, defects of the brake and its control lever and carbon deposition of the turbocharger. If the engine output power is normal, It is necessary to check whether the speed of the hydraulic excavator is inversely proportional to the load during the operation because the flow of the hydraulic pump and the output power of the engine do not match, that is, the product of the flow and the output pressure of the pump is a constant, and the output power of the pump is constant or nearly constant. If the pump control system fails, it is impossible to achieve the optimal matching state of the load of the engine, pump and excavator repair valve in different working conditions, Therefore, the excavator will not work normally. For this kind of fault, the electrical system should be first inspected, then the hydraulic system, and finally the mechanical transmission system.
2. The working speed becomes slow.
The main reason for the slow working speed of the excavator is that the wear of all parts of the whole machine causes the engine power to drop and the hydraulic system to leak. The hydraulic pump of the excavator is a plunger variable pump. After working for a certain time, the internal hydraulic components (cylinder, plunger, port plate, nine orifice plate, turtle back, etc.) of the pump will inevitably be excessively worn, which will cause internal leakage and incongruous data of various parameters, resulting in insufficient flow, high oil temperature and slow working speed, At this time, it is necessary to overhaul the whole machine and repair and replace the parts that wear out of limit. However, if the excavator that has not worked for a long time suddenly slows down, it is necessary to check the following aspects: first, check whether the circuit fuse is open or short circuited, then check whether the pilot pressure is normal, then check whether the servo control valve servo piston is stuck and whether the distributor confluence is faulty, and finally, disassemble the hydraulic pump for data measurement, Confirm the problem of the excavator.
