Working principle of axial piston pump
Working principle of axial piston pump
④ Cylinder bore and plunger pair In order to avoid stress concentration, the edge of the cylinder bore should be polished and rounded; in order to prolong the service life of the cylinder, some of the piston bore are installed with wear-resistant alloy cylinder liner (Fig. f), while others are covered with wear-resistant layer by sintering or other methods; in order to reduce the lateral force, the piston surface used to open an annular groove [Fig. g (a)], but now it seems that it is easy to cause the plunger to be clamped, so the light plunger is mostly used at present . In order to reduce the weight, reduce the inertia force and centrifugal force, and improve the dynamic characteristics of the pump, the plunger is usually made into a hollow form with simple structure. However, the hollow cylinder increases the invalid "dead" volume in the cylinder block, which is not conducive to improving volumetric efficiency and reducing noise, so it is generally filled with light metal or light plastic [Fig. g (b)].
In addition, in order to reduce the leakage of annular gap between plunger and cylinder bore, the clearance of plunger bore is generally controlled within 0.02 ~ 0.04mm.
⑤ When distributing the oil in and out, the valve plate and the auxiliary valve plate on the end face of the cylinder block should bear the eccentric load of the cylinder block due to the accuracy error of adding T and the tilting torque in operation. If the clearance between the cylinder end face and the valve plate is too large, the leakage will be increased and the volumetric efficiency will be reduced, otherwise, the wear of the valve plate will be intensified. The ideal contact condition is that the cylinder block is suspended on the oil distribution plate.
If the gap between the valve plate and the cylinder block is not uniform, it will aggravate the wear of the end face pair of the valve plate and the cylinder block, and affect the performance and service life of the pump. In order to control the uneven clearance, the following measures are taken on the structure of valve plate or cylinder block.
a. Plane distribution is called plane distribution because the combination of valve plate and cylinder block is plane. This structure has the advantages of easy processing and maintenance, axial compensation and so on. Therefore, this structure is widely used in small and medium displacement pumps and motors. For pumps and motors with large displacement, one of the following three measures is usually taken to make up for the uneven gap: one is to use the floating valve plate [Fig. H (a)] to automatically compensate the relative floating of valve plate 1 and flow sleeve 5; the other is to use the floating cylinder block [Fig. H (b)] to automatically compensate the relative floating of cylinder block 2 and flow sleeve 5 In comparison, it is convenient to process and easy to select the compression ratio, but the motion inertia of the cylinder block increases, the self-aligning performance is poor, and the self-priming performance of the pump is affected; third, the floating transition plate [Fig. H (c)] is used to compensate automatically by the relative floating of the transition plate 7 and the cylinder block 2, which is convenient for processing and maintenance, but with less compensation.
For plane valve distribution, sometimes a layer of bronze and other antifriction materials (Fig. f) is used to cover the bottom end face of the cylinder block to reduce the wear of the joint surface between the valve plate and the cylinder block.
b. The spherical port is shown in Figure I. since the joint of port plate 1 and cylinder block 2 is spherical, it is called spherical port. This structure has good self position and can compensate automatically. But the spherical surface processing needs special equipment, high precision and inconvenient maintenance.