Manufacturing technology of swash plate axial piston pump
Manufacturing technology of swash plate axial piston pump
The plunger pump is a kind of hydraulic pump which relies on the reciprocating movement of the plunger in the special cylinder body to achieve oil suction or pressure. The shell only contains, connects and supports the working parts. It is a kind of non pressure bearing hydraulic element. There are two types of piston pumps, axial piston type and radial piston type, with different structures and processes. This section only introduces the material and technology of the key parts of axial piston pump.
(1) The technical requirements are shown in Figure K. the straight shaft axial piston pump is composed of key parts such as transmission shaft 1, swashplate 2, slipper 3, plunger 4, cylinder block 5, valve plate 6, return plate 8, etc. The straight axis axial piston pump can work under high pressure, high speed, high temperature and other harsh conditions for a long time, and has high volumetric efficiency and total efficiency. Therefore, all parts in the piston pump shell should have enough strength and stiffness, and also have high dimensional accuracy and shape accuracy. Therefore, it is necessary to reasonably select the material and heat treatment method of the key parts of the pump, and improve the processing quality, especially the reasonable friction pair material.
(2) Common materials and process requirements of different manufacturers, different specifications of products, the material selection and processing technology are not the same, with the continuous improvement and development of surface treatment technology, the material of hydraulic pump appears the trend of diversification. The combination of various traditional heat treatment technologies and modern surface treatment technologies, including ion implantation, thermal spraying, laser cladding, electrochemical plating, physical chemical vapor deposition and so on, has increasingly shown great technical and economic advantages. In addition, the application of other new engineering materials, such as engineering composite materials and ceramic materials, provides more and more extensive ways for pump material selection and manufacturing.
① Plunger and cylinder block
a. There are two schemes for material and heat treatment of plunger and cylinder: one is hard plunger and soft cylinder; the other is soft plunger and hard cylinder. The first scheme is often used in high pressure and large flow piston pump.
The hard plunger materials are usually 18crmntia, 20Cr, 12CrNi, 40Cr, GCr15, CrMn, 9SiCr
T7a, T8A and nitrided steel 38CrMoAlA. The carburizing depth of the first three kinds of surface should reach 0.8-1.2mm, the quenching hardness should reach 56-63hrc, and the heat treatment hardness of other steels should also reach about 60HRC. CrMn and 9SiCr tool steels have the advantages of small heat treatment deformation and stable microstructure. GCr15 is sensitive to stress concentration after heat treatment, and the plunger has been broken, so it should be used as little as possible. Or various ceramic layers such as ZrO2, Al2O3, Cr2O3 and other ceramic powders can be sprayed or deposited on the surface of the above materials.
The material of cylinder block is usually zqsn10-1 or zqalfe9-4. In addition, wear resistant cast iron or nodular cast iron can also be used. In order to save copper, 20Cr, 12CrNi3A or GCr15 are usually used as the matrix to inlay copper sleeve at the plunger hole, or peek, TORLON, POM and other engineering plastics are used to make cylinder liner structure, namely "combined cylinder block".
If the cylinder block is made of hard alloy steel (hardness up to 60-62hrc), the plunger is usually made of beryllium bronze or qsn10-2-3 tin lead nickel bronze.
b. The process requires that the fit clearance between plunger and cylinder bore should be the minimum sum of leakage and friction loss. When the speed n ＜ 1500r / min and pressure P ＞ 20MPa, it is generally taken as 0.01 ～ 0.015mm. If the speed increases or the pressure decreases below 10MPa, it can be slightly increased.
When the pressure equalizing ring groove is set in the plunger insertion part, the groove size is: depth 0.3-0.5mm, width 0.3-0.7mm, spacing 3-10mm. The groove should keep sharp edge to avoid carrying dirt and to eliminate dirt and particles.
The plunger should be polished after carburizing and quenching. The surface roughness is 0.4 ~ 0.1 μ m, and the tolerance of roundness and taper is less than 1 / 4 of the radial clearance (0.002 ~ 0.005mm).
The surface roughness of the hole is generally 0.8 ~ 0.4 μ m, and the tolerance of roundness and taper is the same as that of the plunger.
② The common material of slipper is wear-resistant copper alloy; several concentric ring grooves are made on the supporting plane of one end of the swash plate, and sometimes silver, indium and other metal antifriction layers are plated. The hydrostatic thrust bearing is formed on the working face of the swash plate by the pressure oil introduced from the center of the plunger; the other end is hinged with the plunger head by rolling ball wrapping process.
③ The working surface of swash plate and pressure plate (return plate) swash plate must be flat, smooth, wear-resistant and have enough compressive strength. Therefore, GCr15 is usually used for swash plate, the hardness after quenching is 58-62hrc, and ZQAl9-4 is usually used for its bearing bush.
18crmnti is usually used for return disk, and the hardness is 60-65hrc after carburizing and quenching. In order to avoid cutting slipper of return disc hole, the hole edge should be rounded about r0.2mm, and the indexing error should be less than 20 '.
④ The material of valve plate should be selected according to the cylinder block. The commonly used material pairs are shown in the table below. Among them, zqsn10-1 and Cr12MoV have the best anti bite ability.
Material matching of lower cylinder block and valve plate
Valve surface of cylinder block
After quenching (or nitriding steel nitriding) of valve plate, in order to stabilize the microstructure, cold treatment and aging treatment are usually carried out.
The surface of bronze cylinder body is sometimes plated with a layer of lead or lead and indium to improve its running in and corrosion resistance.
Some manufacturers spray or sinter engineering plastics such as nylon or peek on the surface of valve plate or cylinder block, and try their best to improve the hardness (50HRC or higher) of the dual surface, or use ceramic coating.
The surface roughness of the valve plate is 0.4 ~ 0.1 μ m, and the flatness tolerance of the valve plate is about 0.005mm, and only concave is allowed, not convex.