5 Main bearing of shield machine 5.1 Bearing type Shield machine is a combination of mechanical, electrical, hydraulic, optical, mechanical, pneumatic, sensing, information, and guidance, and can complete construction processes such as excavation, support, and slag removal, and carry out continuous Tunnel construction equipment that operates in a factory-like assembly line is known as the 'king of construction machinery' and is a major key equipment to measure the level of a country's equipment manufacturing industry. With the full spread of the shield tunneling construction of urban subways, railway tunnels, highway tunnels, water conservancy projects, urban municipal gas pipeline projects, sewage pipeline projects, heating and cooling pipeline projects, and cable pipeline projects in China, the total market demand for shield machines The rapid growth trend also brings a broad market to shield machine bearings. The cutter head is a key component of the shield machine and plays an important role in the tunneling process. The main bearing in the cutter head system is the core part that transmits the driving power and motion. It bears huge axial force, overturning moment and certain radial force during operation. Its performance, life and reliability directly affect the shield machine's performance. Construction progress, safety and mileage. The main bearing of small-sized shield machine usually adopts the structure of four-point contact ball and crossed cylindrical roller, and some have double-row tapered roller structure. The main bearings of shield machine with large quantity and wide area mainly include three-row three-row cylindrical roller combined bearing and three-row four-row cylindrical roller combined bearing. Among them, the most commonly used three-row three-row cylindrical roller combined bearing can be divided into internal gear type. (Fig. 13) and external tooth type (Fig. 14). Fig.13 Inner tooth main bearing for earth pressure balanceshield machineFig.13 Inner tooth main bearing for earth pressure balanceshield machineFig.14 Outer tooth main bearing for mud-water balancedshield machine The function of the main bearing of the shield machine is to support and transmit motion and load. However, due to the extremely low speed of the shield machine, the extremely large and unpredictable load, and the extremely high reliability requirements, the main bearing of the shield machine bears a great burden. Risk, but also put forward strict requirements for its design and manufacture. Due to the inhomogeneity of the geological structure, the size and direction of the tunneling resistance of the shield machine may change drastically. The main bearing of the shield machine often works under extreme conditions such as impact and eccentric load. Technical indicators such as strength, life and reliability are demanding. In addition, it is also required that the main bearing installation part of the shield machine has a reliable seal, and the inside of the bearing has good lubrication. The relevant sealing structure and lubricant need to be specially designed to meet the harsh environmental conditions. 5.2 Technical indicators and key technologies The main technical indicators of the main bearing of the shield machine are: trouble-free use for 10 000 hours (or cumulative excavation of more than 10 km), the axial runout is not more than 0.1 mm, and the operating speed is 1 to 3 r/min. 5.2.1 Design technology 1) Establish a working condition database covering typical geological conditions, formulate steady and unsteady dynamic load spectrums necessary for static strength analysis, dynamic analysis, reliability prediction, performance and life tests, and under special working conditions The ultimate load spectrum, etc. 2) Complete the collection and analysis of the failure data of the main bearing of the shield machine, and compile the failure map under typical working conditions. 3) Carry out research on the lubrication theory and tribology of the shield machine main bearing under low speed, heavy load and impact conditions, study the contact mechanics and dynamic characteristics of the main bearing under steady and unsteady dynamic conditions, and form the corresponding design theory. 4) Carry out theoretical research on the reliability of the main bearing of the shield machine, and establish the reliability theory and remaining life estimation technology of the main bearing under different geological and tunneling conditions. 5) Carry out theoretical research on the strength, stiffness and life design of shield machine main bearings, and optimize the design of main parameters, ideal crown of rollers and raceways, bearing clearance, sealing structure, cage and other structural parameters of parts, as well as performance simulation Development of software for life prediction. 5.2.2 Controllable manufacturing technology 1) Formulate special steel quality control standards for shield machine main bearings, establish a steel quality control system, and realize the 'four modernizations' requirements, that is, intelligent component design, high internal quality purification, and production process Automation and consistency of metallurgical quality. 2) Carry out research on precision heat treatment technology, develop a soft-belt heat treatment process and gear quenching process for simultaneous quenching of 3 raceways, and develop special CNC heat treatment equipment and tooling to improve the consistency and stability of quenching quality; develop products with independent intellectual property rights. Material performance simulation software, dynamic online control and detection technology and surface modification technology. 3) Fully master the precision machining technology of the main bearing parts of the shield machine, and develop the manufacturing technology of super-hard tools such as raceway hard turning technology and CBN.