1. The working principle of hydraulic pump
The working principle of a hydraulic pump is that movement brings about a change in the volume of the pump cavity, thereby compressing the fluid to give the fluid pressure energy. The necessary condition is that the pump cavity has a sealed volume change.
A hydraulic pump is a type of hydraulic component that provides pressurized liquid for hydraulic transmission. Its function is to convert the mechanical energy of power machines (such as electric motors and internal combustion engines) into liquid pressure energy. Its cam is driven by a motor to rotate. When the cam pushes the plunger upward, the seal volume formed by the plunger and the cylinder body is reduced, and the oil is squeezed out of the seal volume and discharged to the place where it is needed through the one-way valve. When the cam rotates to the lower part of the curve, the spring forces the plunger down to form a certain degree of vacuum, and the oil in the oil tank enters the sealed volume under the action of atmospheric pressure. The cam causes the plunger to rise and fall continuously, the sealing volume periodically decreases and increases, and the pump continuously sucks and discharges oil.
There are many factors that affect the service life of a hydraulic pump. In addition to the pump's own design and manufacturing factors, it is also related to the selection of some components related to the use of the pump (such as couplings, oil filters, etc.), and the operation during the test run.
Second, the composition of the hydraulic pump
The hydraulic pump is composed of three parts: coupling, hydraulic oil tank and oil filter.
1. Coupling:
The drive shaft of the hydraulic pump cannot bear radial force and axial force. Therefore, it is not allowed to directly install belt wheels, gears, and sprockets on the shaft end. A coupling is usually used to connect the drive shaft and the pump drive shaft. If due to manufacturing reasons, the coaxiality of the pump and the coupling exceeds the standard, and there is a deviation during assembly, the centrifugal force will increase the deformation of the coupling as the speed of the pump increases, and the large deformation will increase the centrifugal force. Causes a vicious circle, which results in vibration and noise, which affects the service life of the pump. In addition, there are other influencing factors such as loose coupling pins that are not tightened in time, and rubber ring wear is not replaced in time.
2. Hydraulic oil tank:
The main function of the hydraulic oil tank in the hydraulic system is to store oil, dissipate heat, separate the air contained in the oil and eliminate bubbles. The capacity of the fuel tank must be considered first. Generally, mobile equipment takes 2 to 3 times the maximum flow of the pump, and fixed equipment takes 3 to 4 times; secondly, consider the oil level of the fuel tank. When all the hydraulic cylinders of the system extend, the oil level of the fuel tank should not be low. At the lowest oil level, the oil level should not be higher than the highest oil level after the oil cylinder is retracted. Finally, considering the structure of the oil tank, the baffle in the traditional fuel tank cannot play the role of depositing dirt. A vertical baffle should be installed along the longitudinal axis of the fuel tank. There is a space between one end of the partition and the end plate of the oil tank to connect the spaces on both sides of the partition. The oil inlet and outlet of the hydraulic pump are arranged on both sides of the partition at the unconnected end, so that the distance between the oil inlet and the oil return is the farthest. The hydraulic oil tank has more heat dissipation effect.
3. Oil filter:
Generally, pollutants with a particle size of less than 10 μm have little effect on the pump, but when it is larger than 10 μm, especially above 40 μm, it has a significant impact on the service life of the pump. The solid pollution particles in the hydraulic oil can easily aggravate the surface wear of the relatively moving parts in the pump. Therefore, it is necessary to install an oil filter to reduce the degree of oil pollution. Filtration accuracy requirements: 10-15μm for axial piston pump, 25μm for vane pump, 40μm for gear pump. The contamination and wear of the pump can be controlled within the allowable range. At present, high-precision oil filters are widely used, which can greatly extend the service life of hydraulic pumps.