Six key technology upgrading of China gears industry

This part is the main content of gear technology roadmap. This paper analyzes the current situation, challenges and development goals of gear industry from six aspects: gear basic technology, key design technology, key processing technology, gear material and heat treatment technology, lubrication / cooling and sealing technology, and key process equipment technology.

1. Gear foundation technology

(1) current situation

In the aspect of gear profile, the involute gear has been in the leading position because of its advantages such as convenient processing and separable center distance. In recent years, the theoretical research and processing technology research of double circular arc gear are basically in a standstill state. The research of new tooth profiles such as micro line profile and asymmetric tooth profile and new shunt methods has achieved some phased results, which need further research. With the improvement of design means and NC machining technology, the machining of spatial curved surface becomes easier, which lays the foundation for the research and development of better tooth profile. In terms of basic data, foreign research institutions are continuously carrying out basic test research on gear material performance test, load spectrum collection and test, while in China, since the transformation of scientific research institutes, there has been almost no basic test research on gear material and performance test, and there has been little load spectrum collection and test, etc. In terms of test service platform, the gear industry lacks a test service platform with specialized personnel and advanced test equipment to provide test services for the whole industry. In terms of standardization, the standardization system of China’s gear industry is not perfect, the applicable standards of technology and products are few, and the standard implementation rate is low. Many products (such as super large and ultra small module gears) have greatly exceeded the scope of existing standards.

(2) challenge

① With the continuous development of gear transmission in the direction of high power density, high efficiency and low noise, there is an urgent need to research and develop new gear tooth profile and new transmission mode; ② the basic data such as fatigue limit of gear material and load spectrum determine the rationality and reliability of gear product design. The lack of basic research and data has become one of the important factors restricting the design of gear products in China; ③ the lack of a high-level testing service platform for the whole industry, which makes many new gear products unable to get third-party testing and design rationality evaluation, directly affecting product improvement; ④ the gap in standardization leads to low level of design and manufacturing of gear products, low reliability and short service life.

(3) objectives

① Breakthroughs have been made in the research of new tooth profile and new transmission, and some new tooth profile and new transmission with high transmission efficiency, strong bearing capacity and easy manufacturing and testing have been developed; ② relying on professional research institutes and colleges and universities to build public research platforms, increase capital investment, and establish research and achievement sharing mechanisms, Continue to carry out gear basic research including gear material ultimate stress, metallographic organization chart measurement, load spectrum collection, test, etc., establish and continuously improve gear basic database; ③ build a modern gear product test service platform for the whole industry, strengthen the construction of talent team and test capacity, and develop product test standards and specifications, To meet the requirements of product testing, evaluation and service improvement; ④ to establish an advanced and perfect standardization system for the gear industry, so that the gear standardization can enter the ranks of world powers.

2. Key design technology

(1) current situation

The powerful gear technology countries such as Europe, America and Japan continue to improve the design level, power density and reliability of products, and reduce noise and cost through continuous research. In recent years, the design level of China’s gear products has been improving, and the gap between China and advanced countries has gradually narrowed. However, there are still obvious gaps in some aspects, mainly as follows: ① lack of domestic professional software that can realize multidisciplinary coupling design and analysis; ② large deviation in dynamic modeling and dynamic characteristics analysis, low level of vibration reduction and noise reduction design [12]; ③ large gap in multi planetary wheel load sharing design technology, hybrid vehicle power synthesis technology, large ship redundancy confluence and diversion technology [13]; ④ The efficiency and heat balance calculation of gear transmission system are lack of experimental research and calculation basis; ⑤ the integrated design technology of electro-hydraulic composite transmission, which takes auto transmission and speed regulating transmission of ultra supercritical thermal power unit as typical products, is not mastered.

(2) challenge

Due to the obvious gap above, the efficiency, power density and reliability of gear products in China are low, the vibration and noise are large, high-grade gear products such as auto transmission rely on imports, and the transmission devices of some military equipment are blocked by foreign technologies.

(3) objectives

① We will vigorously develop advanced multidisciplinary coupling design and analysis software; ② strengthen dynamics research, combine dynamics design, vibration reduction and noise reduction with gear modification, and improve product grade; ③ conquer the core technology of electro-hydraulic composite transmission, so that the automatic transmission can be manufactured in China and develop zero slip composite transmission; ④ carry out heat balance test research to reduce power loss, To match the strength power and thermal power of the gear transmission device; ⑤ to break through the power shunt, synthesis and redundancy design technology, to solve the power shunt, synthesis and backup problems of important equipment such as ships and aircraft.

3. Key processing technology

The machining here mainly refers to the machining of gear, shaft and other parts. Improving the level of machining technology is an important guarantee to improve the accuracy, quality, reliability and production efficiency of gear products. High precision, high efficiency and environmental protection are the important characteristics of gear processing technology in the future.

(1) current situation

China’s gear manufacturing technology level and manufacturing capacity have been continuously improved, but compared with the international advanced level, gear manufacturing generally has problems such as high energy consumption, low material utilization and production efficiency, poor product quality stability, cutting fluid pollution to the environment, etc. There is a lack of standards and norms in the control of grinding and burn. The enterprises are exploring in their own fields. There is little communication in the industry, and the detection technology can not keep up with it, resulting in high scrap rate and low production efficiency. There is a lack of systematic research in gear superhard machining technology, dry cutting technology, limit (maximum and minimum) manufacturing technology, shot peening strengthening technology and near net forming technology, which is far from meeting the demand.

(2) challenge

Superhard machining and dry cutting can improve machining efficiency and reduce pollution. Gear cold forging and warm forging can save about 30% material and 65% energy. With the aggravation of energy crisis and environmental pollution, it is required that gear product processing should achieve high efficiency, energy saving, material saving, consumption reduction and environmental protection; with the development of mechanical equipment towards high performance, high reliability and long life, it is required that gear product processing should achieve high precision and quality, so a series of key processing technologies need to be conquered.

(3) objectives

① Conquer the near net forming technology and die manufacturing technology of gears, and improve the near net forming rate of automobile gear parts and shaft parts year by year; ② conquer the gear dry cutting and superhard machining technology, and increase the gear dry cutting and superhard machining rate by about 5% annually; ③ carry out the research on repair technology of large gears and other parts, and realize the remanufacturing of large and valuable parts; ④ Study the manufacturing technology of micro parts such as micro gear to meet the demand of ultra small volume transmission device [15]; ⑤ improve the production efficiency and shorten the production cycle by 10% ~ 15% every five years on average; ⑥ study the manufacturing technology of gear to improve the manufacturing accuracy of cylindrical gear and bevel gear.

4. Gear material and heat treatment technology

(1) current situation

① The quality of gear material is low, and there are many defects in casting and forging. Some materials with special requirements, such as high-temperature and high hardness gear steel for helicopter, low-temperature impact resistant gear steel for military vehicles in high cold climate, low stress induction hardening gear steel, etc., are lacking. ② the deformation of gear carburizing and quenching is large, and grinding cracks, burns and grinding steps are easy to occur when grinding teeth, and the carburizing cycle is long and energy consumption is high, It is easy to produce internal oxidation, which affects the bending fatigue strength of the tooth root; the nitriding layer is thin, which is not suitable for gears with large module, if the layer depth is increased, the time is too long, and the phase composition is difficult to control; the induction hardening gear is easy to produce tooth root quenching cracking, and the weak transition layer between the hardening layer and the center causes early fatigue peeling, which seriously affects the bearing capacity and reliability of the gear [16-17].

(2) challenge

The low quality of gear materials, many defects and backward heat treatment technology are the important reasons for the low bearing capacity, low reliability and high rejection rate of gear products in China. More research should be done to change this situation [18].

(3) objectives

① Improve the metallurgical quality of gear steel and casting forgings, reduce the gas content and non-metallic inclusions in steel, the gas content reaches [O] < 10-5, [H] < 2 × 10-6, [n] < 5 × 10-5 respectively, control the hardenability bandwidth of gear steel, the fluctuation of upper and lower limits is less than 3HRC; ② Development of high temperature and high performance steel, low temperature impact resistant steel, high pressure gas quenching micro deformation steel, rapid nitriding steel, precipitation hardening steel and other special performance gear steel; development of high-strength plastic and other non-metallic materials for gears [19]; ③ attack carburizing and nitriding accelerating technology, improve production efficiency, attack deep nitriding technology, improve the bearing capacity of nitriding gear, and expand the scope of application; ④ Study the mechanism and law of stress formation in gear induction quenching process, optimize the quenching process, control the residual stress and overcome the quenching cracking; study the new technology of multi frequency induction heating quenching and induction press quenching; ⑤ study the technology of compound heat treatment tooth surface strengthening, high-energy density hardening and shot peening strengthening, so as to improve the bearing capacity and reliability of gear; ⑥ Research on the technology of gear precise thermomechanical treatment, improve the gear strength and production efficiency.

5. Lubrication, cooling and sealing technology

(1) current situation

China’s gear transmission friction design, development of high-quality lubricating media, research on high-efficiency lubricating cooling technology are significantly behind the international advanced level, and the failure rate of gearbox is high due to lubrication and bearing problems. Oil leakage of gear products is not only common but also serious, which wastes medium and pollutes environment.

(2) challenge

With the development of gear drive to high speed, heavy load, complex service environment and high reliability, the problems of lubrication, cooling and sealing will be more prominent. We must take measures to solve these problems fundamentally.

(3) objectives

(1) develop high quality, multi type and less pollution lubricating media according to different transmission loads and working conditions; second, study solid lubrication, gas lubrication and self-lubricating technology to meet the needs of gear transmission in special service environment; third, study sealing technology, develop various excellent performance and long life seals, simultaneous interpreting oil leakage and frequent replacement of seals. ④ Develop bearings with high bearing capacity, high reliability and long life, change the situation that almost all bearings of high-grade gearbox rely on imports; ⑤ carry out tribological design and oil detection and fault diagnosis technology research.

6. Key process equipment technology

(1) current situation

① Gear cutting machine tools: cylindrical gear machine tools such as gear hobbing machine, gear shaping machine and gear milling machine have a big gap with foreign advanced level in terms of production efficiency, manufacturing accuracy, compounding, and large-scale; the gap between spiral bevel gear machining machine tools is larger, and large spiral bevel gear machining machine tools have developed prototype; ② CNC gear grinding machine: Germany’s CNC forming gear grinding machine is the world leader, Advanced technologies such as automatic tool setting, automatic dressing, on-line measurement and intelligent correction of grinding wheel have been applied. High precision, high efficiency, function compounding and large-scale have become the trend, and the grinding accuracy has steadily reached level 3-5. China’s CNC gear grinding machine has gone through the process from scratch, from existence to precision, but there is still a big gap in reliability, processing efficiency, automatic tool setting, etc., most of the high-grade CNC gear grinding machines still rely on imports; ③ heat treatment equipment: China’s high-grade gear induction quenching machine depends on imports, the carburizing equipment has low automation, high energy consumption, and low level of quenching and cooling equipment, It is difficult to achieve the requirements of process control, energy conservation and environmental protection; ④ tools and tools: gear dry cutting tools, high-efficiency hobbing tools, high-performance CBN tools and grinding wheel are almost all imported; ⑤ measuring equipment: foreign CNC gear measuring centers are widely used, and the measurement accuracy is stable at Level 3; large gear measuring centers and CMM can measure the diameter of 6m gear; Gear on machine measurement system has become a part of the machine tool; gear production line with manipulator automatic loading and unloading gear rapid sorting measuring machine has become the leading equipment of vehicle gear field measurement. The measurement center of medium modulus gear in China is relatively mature, and the measurement accuracy is stable at level 4; the largest gear measurement center can measure gears with a diameter of 2m; the on-line measurement system is in the research and development stage ; the gear rapid sorting measuring machine on the vehicle gear production line has been put into production; there is no coordinate measuring machine that can meet the requirements of gear measurement, Small modulus gear measuring instruments and large diameter gear measuring instruments are almost all imported .

(2) challenge

According to the demand of the future gear product manufacturing for the key process equipment, China must overcome the design and manufacturing technology of the above-mentioned key process equipment in order to focus on the following problems: gear cutting and grinding machine tools focus on solving the problems of high efficiency, high precision, numerical control, compounding, large-scale, automatic loading and unloading, etc; Heat treatment equipment focuses on large-scale, intelligent, efficient, low consumption, environmental protection and other issues; cutting tools and tools focus on Superhard cutting, long life, low cost and other issues; measuring equipment focuses on measuring accuracy, measuring range, in-process measurement, online measurement and other issues.

(3) objectives

① Develop high-precision, high-efficiency and large-scale CNC cylindrical gear grinding machine and bevel gear grinding machine to change the situation that China’s large-scale and high-grade gear grinding machines rely on imports; ② develop dry gear hobbing machine and hard gear hobbing machine, develop special gear milling machine tools such as large-scale bevel gear milling machine; ③ develop high-efficiency gear hobbing tools, develop tool coating materials and technologies, and expand the application of cemented carbide and CBN tools; Develop grinding wheel with high material removal rate, long service life and low dressing frequency; ④ develop high-grade CNC induction hardening machine tool, and develop new intelligent, efficient, low consumption, environmental friendly gear carburizing, nitriding and other heat treatment equipment; ⑤ develop in-situ measurement system of super large gear based on laser tracking measurement technology and indoor IP radar technology, The development of micro gear measuring machine based on optical fiber probe, the development of gear rapid sorting measuring machine combined with manipulator loading and unloading, coupling in the gear production line, etc.

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