The working environment of construction machinery is very bad. Maintenance and maintenance are difficult to meet the requirements of hydraulic system. During operation, there is often a slow and feeble movement of executive element due to the decrease of volumetric efficiency of hydraulic pump. From the characteristics of the structure and movement of the plunger pump can be seen, prone to wear and influence the volumetric efficiency of the following several parts: the end of the cylinder and valve plate wear and tear or injury after the plane gap, sliding shoe and swashplate wear and tear or injury of the plane after the clearance, after the wear ring clearance between the plunger and the cylinder hole. From the analysis of the wear process, once the abnormal wear occurs, the hydrostatic bearing oil film is destroyed, and the particles produced by the wear are difficult to discharge the pump body for a short time, which makes the abrasive participate in the next round of wear, causing a vicious cycle and making the wear speed increase. The most serious parts of wear and tear are cylinder block and port plate, and the floating clearance between slipper and swashplate. The damaged parts are mainly slipper, cylinder end, lining plate and port plate. From the characteristics of gap leakage, smaller clearance plunger and the cylinder hole and the sealing length is large, the influence on the pump efficiency is relatively small; the plane gap and the valve plate and the cylinder end of the sliding shoe and swashplate sealing band is narrow, with the surface strain is the main factor causing the decline in the efficiency of volume. After the failure of the hydraulic pump, the disintegration of the pump should be checked, and the emphasis is on the wear and injury of the above surfaces. For normal wear, no scratches, glued surface parts, after cleaning can be used directly; for mild wear or scratch parts, grinding and polishing can be repaired; for valveplate serious strain, damage and yellowed parts by grinding, after grinding can not meet the requirements of assembly, taking into account the maintenance the cost and time, recommended replacement parts. Axial piston pump is an important power element and executive element in hydraulic system. It is widely used in the field of industrial hydraulics and walking hydraulics. It is one of the most widely used hydraulic components in modern hydraulic components. Because of the complicated structure of the axial piston pump and the high requirement for the manufacturing process and material, it is one of the hydraulic components with high technical content. At present, the domestic piston pump has a relatively high demand for medium. Therefore, when driving the fire resistant and phosphate ester hydraulic fluid, the effect of pump is stamina, but the technology abroad is relatively mature.

1 泵体内部结构分析

Internal structure analysis of 1 pump body

轴向柱塞泵可分为斜盘式和斜轴式2大类。在变量形式上，斜盘式轴向柱塞泵靠斜盘摆动变量，斜轴式轴向柱塞泵则为摆缸变量。斜盘式轴向柱塞泵有通轴和半轴2种结构，其中通轴型在液压行业使用比较广泛。通轴型斜盘式轴向柱塞泵的结构特征如图所示。

The axial piston pump can be divided into 2 types: inclined disk type and inclined shaft type. In the form of variable, the inclined disk axial piston pump depends on the swing variable of the inclined disk, and the skew axial piston pump is the variable of the pendulum cylinder. The inclined disk axial piston pump has 2 kinds of structure, which are through shaft and half axis, of which the shaft type is widely used in the hydraulic industry. The structure features of the axially inclined axial piston pump are shown in the diagram.

该泵的主轴采用了两端支承，斜盘通过柱塞作用在缸体上的径向力可以由主轴轴承受，因而取消了缸体外缘的大轴承; 该泵无单独的配流盘，而是通过缸体和后泵盖端面直接配油。缸体中孔内的弹簧的作用与非通轴型泵的相同，是将缸体压向右侧配流端面,保证启动时的密封。通轴泵结构的另一特点是在泵的外伸端可以安装一个小型辅助泵(通常为内齿轮泵) ，供闭式系统补油之用，因而可以简化油路系统和管道连接，有利于液压系统的集成化。这是近年来通轴泵发展较快的原因之一。此外，通轴驱动是一种坚固设计，通轴驱动选项便于安装控制装置，附加装置或其他的辅助泵。它能安装同样规格的第二个泵，这就提供了真正的串联泵的结构。

The main shaft of the pump is supported by two ends. The radial force of the swashplate acting on the cylinder body can be sustained by the spindle shaft through the plunger. Therefore, the large bearing on the outer edge of the cylinder body is cancelled. The pump has no separate distributor, but directly matches the oil through the cylinder block and the rear pump cover end. The function of the spring in the hole in the cylinder is the same as that of the non - shaft type pump. It is to press the cylinder body to the right side of the flow face to ensure the sealing of the start. Another feature of the shaft pump structure is that a small auxiliary pump (usually internal gear pump) can be installed at the extended end of the pump, which can be used for the closed system to replenishing oil, so that the connection between the oil system and the pipeline can be simplified, and the integration of the hydraulic system will be beneficial. This is one of the reasons for the rapid development of the shaft pump in recent years. In addition, the through axis drive is a solid design, and the through axis drive option is convenient for installation of control devices, additional devices or other auxiliary pumps. It can install second pumps of the same specification, which provides the real structure of the series pump.

1.1 缸体端面间隙的自动补偿

Automatic compensation for end gap of 1.1 cylinder block

使缸体紧压配流盘端面的作用力，除弹簧的推力外，还有柱塞孔底部台阶面上所受的液压力，此液压力比弹簧力大得多，而且随泵的工作压力增大而增大。由于缸体始终受力而紧贴着配流盘，就使端面间隙得到了自动补偿，提高了泵的容积效率。

The force acting on the end surface of the valve body is tightly pressed. Besides the thrust of the spring, there is also the liquid pressure on the bottom step surface of the plunger hole, which is much larger than the spring force and increases with the increase of the working pressure of the pump. As the cylinder body is always stressed and clinging to the flow plate, the end gap is automatically compensated and the volume efficiency of the pump is improved.

1.2 柱塞头接触方式

Contact mode of 1.2 plunger head

轴向柱塞泵在工作时由于柱塞球头与斜盘平面理论上为一点接触，因而接触应力大，极易磨损。一般轴向柱塞泵都在柱塞头部装一滑履，二者之间为球面接触，而滑履与斜盘之间又以平面接触，从而改善了柱塞工作的受力状况。并且由于各相对运动表面之间通过小孔引入了压力油，实现可靠的润滑，故大大降低了相对运动零件表面的磨损。这样，就有利于泵在高压下工作。

When the axial piston pump is in contact with the plane of the plunger head and the inclined plate, the contact stress is large and it is very easy to wear. In general the axial piston pump plunger head mounted sliding shoe, between the two spherical contact and sliding between the shoe and the inclined plate with surface contact, thereby improving the work force of the piston. Moreover, due to the introduction of pressure oil through the small holes between the relative moving surfaces to achieve reliable lubrication, the wear of the relative moving parts is greatly reduced. In this way, it is good for the pump to work under high pressure.

1.3 滑靴的静压支撑结构

Static pressure support structure of 1.3 slipper

如图所示，滑靴是按静压轴承原理设计的，缸体中的压力油经过柱塞球头中间小孔流入滑靴油室，使滑靴和斜盘间形成液体润滑，改善了柱塞头部和斜盘的接触情况，有利于提高轴向柱塞泵的压力。柱塞由斜盘上的滑靴轴承静压平衡，有效地提供无脉动流量。

As shown, slipper is designed according to the principle of hydrostatic bearing, the oil pressure in the cylinder by the piston ball head into a small hole in the middle of the slipper oil chamber, the liquid lubrication form slipper and swash plate, improve the contact condition of plunger head and the swash plate, improve the pressure of axial piston pump. The plunger is balanced by the static pressure of the slipper bearing on the inclined plate to provide no pulsating flow effectively.

1.4 壳体内的泄油压力

Oil relief pressure in 1.4 shells

壳体内的泄油压力取决于轴封所能允许的最高压力。德国REXROTH 公司生产的斜轴式轴向柱塞泵和马达的壳体泄油压力一般为012 M Pa，也有高达1 MPa的(如A2F定量泵系列)，国产轴向柱塞泵和马达的壳体泄油压力应严格遵照产品使用说明书的规定，过高的壳体泄油压力将导致轴

The oil discharge pressure in the shell is determined by the maximum allowable pressure in the shaft seal. The German company REXROTH axial plunger pump and motor oil pressure is 012 M Pa, there are up to 1 MPa (such as A2F, a series of quantitative pump) of domestic axial piston pump and motor oil pressure shall be in strict accordance with product instructions, a high relief the oil pressure will cause the shaft