Analysis of underspeed problem of hydraulic power unit
The hydraulic power unit is a system that provides power to the hydraulic press. It cannot underspeed. If underspeed, it will cause insufficient power and affect normal work. Let’s look at the problem of hydraulic power single underspeed:
One, hydraulic power unit underspeed elimination method
1) Eliminate the failure of insufficient output flow and low output pressure of the oil pump:
2) Eliminate the pressure failure caused by pressure valves such as overflow valves:
3) Find out the crossbow that produces internal leakage and external leakage, eliminate internal and external leakage: replace severely worn parts to eliminate internal leakage;
4) Control oil temperature;
5) Clean parts such as flow valves, and change the oil in time when oil pollution is serious;
6) Find out the reason for the air intake of the hydraulic power unit and remove the air in the hydraulic power unit.
Two, reasons for underspeed of hydraulic power unit
1. During work feed, the work feed speed is significantly reduced under load, even if the speed control valve (throttle valve, etc.) is opened.
1) There is air in the hydraulic power unit.
2) Impurities mixed in the oil block the orifice of the flow control valve, causing the working speed to decrease; when the oil is blocked, the speed is unstable;
3) The design of the hydraulic power unit is unreasonable. When the load changes, the flow into the actuator of the hydraulic equipment also changes, causing a change in speed:
4) The system oil temperature increases, the oil viscosity decreases, the leakage increases, and the effective flow decreases;
5) When the system is under load, the working pressure increases and the leakage increases, and the adjusted speed decreases due to the increase of internal and external leakage:
2. Reasons for insufficient speed of fast movement
1) Large resistance during fast forward: For example, the guide rail is lubricated and the oil is cut off, the guide rail's insert pressure plate is adjusted too tightly, and the installation accuracy and assembly accuracy of the oil cylinder are poor, causing the friction resistance to increase during fast forwarding.
2) The internal and external leakage of the system is serious: the working pressure is generally lower during fast forward, but it is much higher than the oil return pressure. When the piston seal of the oil cylinder is damaged, the two cavities of the oil cylinder leak large due to the series of cavities (there is a pressure difference), which makes the fast movement speed of the oil cylinder insufficient, and the internal and external leakage of other parts will also cause this phenomenon;
3) The overflow valve is deformed or installed as a weak spring due to spring deformation or wrong installation, the main spool orifice is partially blocked, and the main spool is stuck in the small opening position. As a result, part of the pressure oil output by the oil pump overflows back to the tank, making it open The effective flow of the system to the actuator is greatly reduced, making the rapid movement speed insufficient
4) The output flow of the oil pump is not enough and the output pressure is not increased;
Third, the adverse effects of hydraulic power unit underspeed
The underspeed of hydraulic equipment's executive components (oil cylinder and oil motor) includes two situations: one is that the speed is not fast enough during fast movement (fast forward), and it will not reach the design value and the specified value of the new equipment; the other is that it works under load The speed (work advance) decreases significantly as the load increases.
Especially for large-scale liquid equipment and equipment with heavy load, this phenomenon is particularly significant, and the speed is generally related to the flow rate.
Under-speed first affects production efficiency and increases the cycle time of hydraulic equipment; under-speed phenomenon often stops moving under heavy loads, which will affect whether the equipment can work normally. For equipment that requires rapid movement, such as a surface grinder, the speed is not enough to affect the surface roughness of the grinding.