Axial plunger pumps are generally composed of main parts such as cylinder block, oil distribution plate, plunger and swash plate. There are multiple plungers in the cylinder, and the plungers are arranged axially, that is, the centerline of the plungers is parallel to the axis of the drive shaft, so it is called an axial plunger pump. But it is different from the reciprocating plunger pump, because its plunger not only reciprocates in the pump cylinder, but also the plunger and the pump cylinder rotate relative to the swash plate. The plunger contacts the swash plate with a spherical end. There are high and low pressure moon-shaped grooves on the oil distribution plate, which are separated from each other by a partition wall to ensure a certain degree of sealing. They are respectively connected with the oil inlet and the oil outlet of the pump. There is an inclination angle between the axis of the swash plate and the axis of the cylinder.
The working principle of the axial plunger pump is when the motor drives the drive shaft to rotate, the pump cylinder and the plunger rotate together, and the plunger head always keeps in contact with the swash plate, because the swash plate and the cylinder block are at an angle. , So when the cylinder rotates, the plunger reciprocates in the pump cylinder. Take the next plunger in Figure l-40 as an example. It turns from 0° to 180°, that is, to the position of the upper plunger. The volume of the plunger cylinder gradually increases, so the liquid is sucked through the suction port a of the oil distribution plate. When the plunger turns from 180° to 360°, the volume of the plunger cylinder gradually decreases, so the liquid in the cylinder is discharged through the outlet of the oil distribution plate. As long as the drive shaft continues to rotate, the pump will continue to work.
By changing the angle of the tilting element, the stroke length of the plunger in the pump cylinder can be changed, and the flow rate of the pump can be changed. The fixed inclination angle is called a quantitative pump, and the inclination angle can be changed is called a variable pump.
Axial plunger pump has two types, swash plate type and slanted shaft type, according to the different tilting elements.
swash plate type is that the swash plate has an inclination angle relative to the rotating cylinder, which causes the plunger to reciprocate in the pump cylinder. The axis of the drive shaft is consistent with the axis of the cylinder. This kind of structure is relatively simple, the speed is high, but the working conditions are high, and the contact part between the end of the plunger and the swash plate is often a weak link. The axis of the swash plate of the inclined axis type is consistent with the axis of the drive shaft. It is because the plunger cylinder is inclined at an angle relative to the drive shaft to make the plunger move back and forth. Flow adjustment is realized by the angle of the swing plunger cylinder, so some are also called swing cylinder. Compared with the swash plate type, it works reliably, has a large flow, but has a complicated structure.
Compared with the radial piston pump, the axial piston pump has a higher discharge pressure. It can generally work in the range of 20-50 MPa, with high efficiency, small radial size, compact structure, small volume and light weight. However, the structure is more complicated than the radial piston pump, the processing and manufacturing requirements are high, and the price is more expensive.
Axial plunger pumps are generally used in hydraulic transmission systems of machine tools, metallurgy, forging, mining and hoisting machinery, and are especially widely used in high-power hydraulic transmission systems. In order to improve efficiency, gear pumps or sliding vane pumps are usually used as auxiliary oil pumps in applications to supply oil, make up for leakage and maintain a certain pressure in the oil circuit.
