Study on the efficiency of gear transmission

Gear transmission is the most common mechanical transmission in modern machines. It is a main form of transmission of machine power and motion and an important basic part of mechanical products. Compared with belt, chain, friction, hydraulic and other mechanical transmission, it has a series of characteristics, such as large power range, high transmission efficiency, high peripheral speed, accurate transmission ratio, long service life, small structure size, etc. Therefore, it has become an indispensable transmission part of many mechanical products, and it is also the transmission form with the largest proportion in the machine. The design and manufacturing level of gears will directly affect the performance and quality of mechanical products. Due to the position and role of gear transmission in the machinery industry and even the whole national economy, gear is recognized as a symbol of industry and industrialization.

Gear transmission technology has experienced a long history of development. From 400 to 200 B.C., gears were used in ancient China. The bronze gears unearthed in Shanxi Province of China are the oldest gears that have been found so far. As a guide car reflecting the achievements of ancient science and technology, it is a mechanical device with gear mechanism as the core. But from the end of the 17th century, people began to study the tooth shape that can transmit the motion correctly. In the 18th century, after the European industrial revolution, the application of gear transmission became more and more extensive. First, cycloid gear was developed, then involute gear. As early as 1694, Philippe de la hire, a French scholar, first proposed that the involute can be used as the tooth curve. In 1733, Camus M. of France proposed that the common normal line of tooth contact point must pass through the node on the central line. He considered the meshing state of two tooth surfaces and established the concept of contact point trajectory. In 1765, Euler L. of Switzerland put forward the mathematical basis of the new analytical study of the tooth profile of the involute gear, and clarified the relationship between the curvature radius of the tooth profile curve and the position of the curvature center of a pair of meshed gears. Later, Savary further completed this method and became the present Euler Savery equation. It is Robert Willis who contributed to the application of involute profile. He proposed that when the center distance changes, the involute gear has the advantage of constant angular speed ratio. In 1873, Hoppe, a German engineer, put forward the involute tooth shape when the pressure angle changes for the gears with different tooth numbers, so as to lay the ideological foundation of modern modified gears.

However, the gear has high requirements for manufacturing and installation accuracy, and the development of gear application has been relatively slow. Until the end of the 19th century, the principle of the method of generating gear and cutting gear was found. The method of generating gear by using the method of generating gear not only has high machining accuracy, but also has high production efficiency. It is suitable for mass production. This method improves the means of gear processing, involute gear shape shows great advantages, gradually replacing cycloid gear as the most widely used gear. When cutting teeth, as long as the cutter is moved slightly from the normal meshing position, the corresponding shift gears can be cut on the machine tool with standard gear cutter. In 1908, Maag company of Switzerland researched and manufactured the gear shaper processed by Zhancheng method. Then, BSS of UK, AGMA of USA, din of Germany and so on have put forward a variety of calculation methods for the modified gear. In order to improve the service life of power transmission gear and reduce its size, Humphris, an Englishman, first published the idea of circular tooth shape in 1907. In 1926, willhaber, a Swiss, obtained the patent right of normal circular arc helical gear. In 1955, Novikov, the former Soviet engineer, came into industrial application after finishing the practical research. In 1970, student, an engineer of Rolls Royce company in the UK, obtained the American patent for double circular arc gear. At the same time, China, the former Soviet Union, Japan and other countries have carried out a series of development and Research on the double arc tooth profile, and obtained the general application results.

Although digitalization, networking and intelligence have been applied in the foundry industry in China, there is still a big gap compared with foreign countries. There are few funds, technologies and personnel for independent research and development of software in China. The ability of independent research and development of commercial casting simulation software is still weak, the market share of software is not high, and the world influence is even less. The application of casting process numerical simulation software and rapid casting technology in domestic foundry enterprises is not popular enough, the application level is relatively low, the application of robot is very few, the application of Internet of things + technology is just beginning, and there is a big gap with foreign advanced foundry enterprises. In the large-scale foundry enterprises, the numerical simulation software of casting process is generally purchased, and the simulation technology is used in the development of new products to a certain extent. The simulation results play a certain role in the formulation and optimization of new product development process. However, the understanding of simulation is still relatively shallow, the level of simulation application personnel is still relatively low, the performance parameter database of simulation matching is still very lacking, and the situation of the self-contained database of software is not completely consistent with that of the enterprise. Therefore, there are many misunderstandings about simulation. For example, some people think that the simulation results are quite different from the actual results, and they deny the simulation completely without asking for any questions. Some people blindly believe in the simulation results, and directly adopt the guidance of production without in-depth analysis and judgment. All of these affect the popularity and depth of simulation technology in the foundry industry.

Intelligent manufacturing generally refers to intelligent manufacturing technology and intelligent manufacturing system, which is the product of the combination of artificial intelligence technology and manufacturing technology. In China’s 12th Five Year Plan for the development of Intelligent Manufacturing Science and technology, intelligent manufacturing is defined as “information manufacturing facing the whole life cycle of products and realizing ubiquitous perception. It is based on advanced technologies such as modern sensing technology, network technology, automation technology and anthropomorphic intelligent technology, and through intelligent perception, human-computer interaction, decision-making and execution technology, Realize the intelligent design process, manufacturing process and manufacturing equipment. Finally, the intelligent manufacturing system should change from the human-machine harmonious system which is the core of human-machine decision-making to the autonomous operation which is the main body of machine. Of course, intelligent manufacturing has other different definitions. However, no matter from which aspect, there is still a big gap between China’s foundry industry and intellectualization. With the development of technology, many enterprises have used robots or manipulators. The equipment of molding, core making, sand dropping and other processes in foundry enterprises has realized semi-automatic and automatic production. But so far, there are still many casting enterprises with backward equipment, following the traditional manual production mode, and there is a considerable gap compared with the goal of building an intelligent casting factory. One of the preconditions for building a digital foundry is that the equipment equipped by the enterprise must have the characteristics of automation and intelligence.