The roller assembly is one of the walking parts of mining machinery such as excavators. On the one hand, it plays the role of supporting the weight of the whole machine in the excavator. On the other hand, it is also the guide rail of the chain rail assembly in the walking part. The relative movement of the rail assembly plays a guiding role. At the construction site of the excavator, the phenomenon of leakage of the roller assembly from different parts often occurs, and once the oil leakage occurs, the construction must be stopped and the roller assembly must be replaced with a new one, if it is not replaced in time , The internal parts of the roller will be seriously worn out, leading to the failure and scrapping of the roller, affecting the normal work of the excavator and the production efficiency of the construction, and also causing great economic losses to the construction party due to the shutdown. Therefore, the analysis caused the roller The reason for the oil leakage of the assembly, it is very important to take corresponding countermeasures, check the leaks and fill the vacancies, and prevent the oil leakage of the rollers.

　　1 Analysis of oil leakage parts of roller assembly

　　Take the EX200 excavator roller assembly shown in Figure 1 as an example to analyze its basic components, sealing parts and oil leakage parts. When working, the shaft seats at both ends, together with their float seal rings, float seal rings and shaft and the O-ring seal on the shaft, are fixed on the frame of the excavator, while the wheel body and float seal rings at both ends, The float seal ring and the bimetal bushing rotate around the shaft together to ensure that the bushing and the shaft form sliding friction. In order to reduce friction and wear, a certain amount of lubricating oil is added to the inner cavity of the roller assembly through the oil injection hole on the shaft seat at the time of assembly, and then sealed by an oil plug. During the work of the track roller assembly, due to various reasons, the lubricating oil in the inner cavity will leak from several parts, there are three main parts: ① the large openings at both ends. Corresponding sealing parts are the contact surface between the two floating seal rings and the floating seal rubber ring, wheel body and shaft seat; ②the shaft ends at both ends. The corresponding sealing parts are the shaft and the shaft seat and the O-ring seal; ③ the oil plug on the shaft seat at one end. The corresponding sealing parts are the oil holes on the oil plug and the shaft seat. When these seal parts fail to seal, oil leakage will occur, and the following analysis will be conducted according to the oil leakage parts.

　　Figure 1 Assembly diagram of EX200 roller assembly

1. Shaft seat 2. Wheel body 3. Floating sealing ring 4. Floating sealing ring 5. Bushing 6. Shaft 7. O-shaped sealing ring 8. Pinch pin 9. Oil plug Ⅰ. Large opening at both ends Ⅱ. Shaft At the head (both ends) Ⅲ. At the oil plug

   
   

　　2 Causes and countermeasures of oil leakage at large mouth

　　The large mouth refers to the space between the wheel body and the shaft seat, see Figure 1. After the assembly of the roller assembly or when it has been installed on the main engine to work, this is the most common location where oil leakage occurs, and the cause of oil leakage is more complicated. After years of analysis and practice, it was found that the main reason is improper sealing between the two floating seal rings, and secondly due to improper sealing between the floating seal rubber ring and the wheel body or between the floating seal rubber ring and the shaft seat.

　　(1) Oil leakage between two floating seal rings

　　The two floating seal rings are used in pairs in the roller assembly. During assembly, the floating seal ring on the floating seal ring gives a certain pressure to the 1 floating seal ring through the wheel body and the shaft seat, so that 2 pairs The surface of the floating seal ring is in contact with each other, and it is always in a floating state during work, called floating seal ring and floating seal rubber ring. As shown in Figure 2. it is a partially enlarged view of the two floating seal rings. When the roller is working, 2 pairs of floating seal rings rotate relatively, and a part of the lubricating oil will enter the contact surface of the two floating seal rings, and on the two contact surfaces An oil film is formed, that is, a mixed lubrication state that has both boundary lubrication and liquid lubrication is formed between the two contact surfaces. In this state, no oil leakage will occur. When the dry friction and boundary friction coexist between the two contact surfaces, it will cause this point.Under the effect of dry friction, the lubrication will fail, the wear will increase, and the lubricant will leak from this point. Out. The reasons for this phenomenon are the pressure between the two floating seal rings, the processing quality and surface cleanliness of the floating seal rings, the assembly quality, and the viscosity of the lubricating oil.

　　Measures to prevent oil leakage at the two floating seal rings: ① When designing the product, the dimensions of each part in the assembly should be designed according to the corresponding standard requirements to ensure that the two floating seal rubber rings have a reasonable pressure on the two floating seal rings after assembly; ②When processing the two floating seal rings, the final grinding should be carried out in pairs to ensure that the contact surface has a small surface roughness value, and the grinding should be packaged in pairs and used in pairs during assembly to ensure that the two contact surfaces are even after assembly Contact; ③ The surface of the two floating seal rings should be kept clean during assembly, no dust and impurities can enter; ④ The floating seal rubber ring should not be twisted during assembly; ⑤ Add lubricating oil of appropriate viscosity, and use different lubricating oils in winter and summer.

　　Figure 2 Partial enlarged view of two floating seal rings

　　(2) Oil leakage between the floating seal rubber ring and the wheel body or shaft seat

　　The oil leakage at the large mouth is not always from the contact surface of the two floating seal rings. In the production practice, it is sometimes found that the oil leaks from the contact between the floating seal rubber ring and the wheel body or the shaft seat. Oil leakage at this part is relatively easy to judge. The overall achievement of disassembling the oil-leakage roller will be found that the installation of the floating seal rubber ring is twisted or the hardness of the floating seal rubber ring is too high, the elasticity is poor, or the processing quality of the wheel body or shaft seat is poor, such as size The precision is low or the surface roughness value is too large. Therefore, in order to avoid oil leakage here, the following measures are taken: ① During assembly, it must be ensured that the floating seal rubber ring cannot be twisted; ② When manufacturing the floating seal rubber ring, it should be manufactured according to product design requirements to ensure that it has sufficient Elasticity; ③ Improve the processing quality of the wheel body and shaft seat.

　　In order to prevent oil leakage at the large mouth and avoid the serious consequences of oil leakage from the assembly to the host, the oil should be run in after the assembly is filled with oil, that is, a special device is used to simulate the state of the assembly on the host to make the assembly good. The roller assembly is operated under a certain load, and the operation is carried out for 3 minutes, so that the floating seal assembly can be in a good lubrication and sealing state.

　　3 Reasons and countermeasures for oil leakage at the shaft head

　　The shaft head refers to the area between the shaft and the shaft seat, see Figure 1. After the roller assembly is assembled or when it has been installed on the main machine to work, this is also a common part of oil leakage. The cause of oil leakage is relatively simple. Through practical analysis, the seal between the shaft and the shaft seat and the O-ring seal failed: ① During assembly, the O-ring was twisted on the shaft; ② During assembly, the O-ring was partially bitten by the shaft seat. In order to avoid the above phenomena, the following methods are adopted: ①When assembling, ensure that the O-ring seal is installed correctly and no distortion occurs; ②Before assembly, the burrs on the shaft and the shaft seat should be removed to avoid puncturing the O-ring seal; ③The shaft seat When designing, the hole at one end of the shaft should be rounded, as shown in Figure 3 (a). Practice has proved that if the chamfer shown in Figure 3 (b) is used, or there is no rounding at the 10° chamfer, the O-ring seal on the shaft after assembly is likely to be gnawed, so the design should be sufficient Consider the influence of the structure of the shaft seat on the sealing performance.

　　Figure 3 Partial structure diagram of shaft seat

　　4 Reasons and countermeasures for oil leakage at the oil plug

　　The oil plug refers to the connection between the oil plug and the oil hole of the shaft seat, see Figure 1. After the assembly of the EX200 roller assembly, the oil plug is screwed into the oil hole of the shaft seat for sealing. This oil plug and oil hole Pipe threads designed to be sealed with threads will normally seal well, but if the thread machining accuracy is low, oil will leak from here. In order to avoid oil leakage here, on the one hand, it is to improve the machining accuracy of the internal and external threads, and to improve the matching accuracy of the thread pair; on the other hand, to ensure safety, the raw material tape should be wrapped around the oil plug to ensure reliable sealing.

　　5 Conclusion

　　Through the analysis of the cause of oil leakage of the roller assembly and the countermeasures to avoid the generation of oil leakage, it has been proved by production practice that the correct cause is found and appropriate measures are taken to effectively prevent the oil leakage of the roller assembly. .