Analysis on the cause of oil leakage of high press

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The electronic injector system can be divided into electronic pump nozzle system and electronic common rail system

the nozzle system of the electric control pump is an improved type based on the PT oil supply system, which uses the opening and closing of the solenoid valve on the injector to control the amount of oil entering the oil cup and removes the governor. The way of pumping oil is still to press the plunger with the rocker arm, which is the same as the PT oil supply system. The electronically controlled common rail system is equipped with a fuel rail on the cylinder head. The fuel rail is a long tubular closed container, and the fuel injectors of each cylinder are installed on the container to use this fuel rail together, which is the so-called common rail. The fuel pump continuously pumps diesel oil into the common rail through the check valve to generate high pressure, which is similar to the air tank of the braking system. The pressure sensor feeds back the pressure value in the common rail to the control unit, and regulates the pressure in the common rail by controlling the proper opening and oil drainage of the solenoid valve. The pressure in the common rail is the injection pressure of the fuel injector, which can reach 100~120 MPa. The way of oil pressure generation is completely different from that of plunger pump. The fuel supply timing is controlled by the opening time of the injector solenoid valve, and the fuel injection quantity is controlled by the continuous opening time of the solenoid valve, so the system does not need an advance device or a governor. The normal operation of the system requires that the injector solenoid valve must be able to open and close on time, quickly and reliably, and can withstand long-term high-frequency opening and closing conditions. Electronically controlled diesel has good power performance, fuel saving, and smokeless and blackened when accelerating, but the cost of the electronic control device is high

this paper analyzes the causes of the oil leakage problem of the high pressure oil pipe of 20/27 diesel engine, puts forward the improvement measures, and introduces the test and application results 1 overview Sichuan diesel engine plant is one of the imported manufacturers of 20/27 series diesel engines. The high-pressure oil pipe of diesel engine is an important part of diesel engine. It connects the high-pressure oil pump and injector, and the maximum working oil pressure can reach more than 100MPa. The conical seal of high-pressure oil pipe connection is not reliable, resulting in leakage, which directly affects the performance of diesel engine. See Figure 1 for the installation diagram of 20/27 diesel engine high pressure oil pipe. The connecting cone of high-pressure oil pipe is formed by cold upsetting, and it is not processed after upsetting. In the process of using domestic materials to make the high-pressure oil pipe of 20/27 diesel engine, the factory solved the technical problems such as insufficient upsetting and broken ends. However, the self-made high-pressure oil pipe has not been used for a long time, and a considerable part of the connecting conical surfaces at both ends have oil leakage, but it has not been well solved. 2 cause analysis the domestic material brand used by the 20/27 diesel engine high-pressure oil pipe factory is 16Mn, and the German high-pressure oil pipe material brand is st52.4nbk. There is no obvious difference in the performance of the two materials. It can be seen from the installation diagram of the high-pressure oil pipe of this model that the oil leakage in the connection part of the high-pressure oil pipe may be caused by the high-pressure oil pipe. The project has carried out the production technology development of UHV transmission insulation structural parts, the production technology development of cross-linked polyethylene UHV insulation materials, the scope preparation technology development of high-performance boron carbide ceramics, the preparation technology development of boron carbide based nuclear protective materials, the development and utilization of special porous ceramics and their composites It is caused by the development and production of key technologies for the industrialization of high-performance copper-clad aluminum conductor materials, and the loose sealing of the connecting sealing cone of fuel injectors and high-pressure oil pumps. Through inspection, the high-pressure oil pump and fuel injector are excluded. After inspection, the cold heading conical surface of the finished high-pressure oil pipe also conforms to the drawing, but there is a certain error in the bending size, which will produce additional stress on the installation. Due to the vibration of high-pressure oil pipe and the installation stress caused by the bending error of high-pressure oil pipe, the sealing surface is not tightly sealed. Through the enlarged projection inspection of the sealing cone of high-pressure oil pipe, compared with the hp-rtm solution, it is found that the cone is slightly incomplete, the surface shape is irregular, and some sealing cones of high-pressure oil pipe have slight bumps, which is caused by mutual collision during the transportation and stretching of parts. These all lead to the problem of leakage due to the loose sealing of the connecting surface of the high-pressure oil pipe after installation. Therefore, the main reason for the oil leakage of the high-pressure oil pipe of the diesel engine is the small shape error of the sealing cone of the high-pressure oil pipe, and the bending error is the secondary reason. 3 measures the subtle shape of the sealing cone of high-pressure oil pipe is incomplete, which is mainly caused by some uncertain factors in the process of cold heading filling. After several schemes of mold and cold heading process are tested, the effect is not obvious. In order to ensure the accuracy of the shape and size of the sealing cone, a finishing grinding process is added after the cold heading of the high-pressure oil pipe connecting head and before the bending of the oil pipe. Through grinding, the accuracy of the size and shape of the cone is guaranteed. The grinding test shows that almost every high-pressure oil pipe needs to be ground by 0.02mm ~ 0.05mm to form a complete and accurate cone, and some of them need to be ground by more than 0.1mm. This also explains why a small number of high-pressure oil pipes leak when they are installed and tested in the factory. At the same time, in order to prevent the sealing cone of the high-pressure oil pipe from being damaged due to the collision of parts in the subsequent processing, transportation and storage process, a special protective sleeve for the high-pressure oil pipe is designed. After the cold heading, the protective sleeve is put on, which completely solves the problem of parts being damaged. At the same time, the bending die and process are improved to reduce the bending error. The bench test and the actual use of users have proved that the reliability of the high-pressure oil pipe with the improved process has been greatly improved, and the problem of oil leakage due to the loose sealing of the high-pressure oil pipe of the machine has been basically solved, which shows that it is feasible to use the method of grinding and supplementary processing to solve the problem of micro out of tolerance of the surface dimension of cold heading parts with high requirements

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