New technology and development trend of automotive gear processing

Along with the continuous development of China's economy, the automobile manufacturing industry also develops rapidly. In the processing and production of the automobile industry, the automobile gear is constantly progressing. In the traditional system of the car, the car gear belongs to one of the very important parts, so the quality of the car gear itself has a direct impact on the quality of the traditional system. Not only that, automotive gears will also have a direct impact on the overall function of the car and noise, so it is crucial to analyse the new processing technology and development trends of automotive gears.
　　I. Introduction

　　Nowadays, the car in people's real life as an indispensable means of transport, its function is highly concerned. In automotive processing production, gears belong to the basic transmission components. Along with people's increasingly high requirements for the car, the quality of gears and their functions are highly valued. Gradual improvement of gear processing technology is conducive to the positive improvement of gear strength, in order to ensure that the gear has noise reduction and durability function, but also to ensure that the stability of the car to improve, so as to extend the use of the car cycle and overall comfort.

　　Second, gear processing dry cutting technology

　　All along, automotive gear cutting process are using cutting oil, which will not only pollute the industrial production environment, but also a significant threat to the operator's own health. In addition, the use of cutting oil will increase the related costs, such as the cost of waste oil treatment, cutting oil costs, separation of oil mist equipment. These will further increase the cost of processing, some countries in the treatment of cutting oil costs even more than 10-30% of the total processing costs. Therefore, under the environmental protection requirements, automotive gear processing plants in many countries advocate the use of cutting oil-free dry cutting technology. In order to ensure that dry cutting is practicable, the first step is to strengthen the research and development of dry cutting machine tools and tools required for the foundation. In the dry cutting technology required tools, to ensure that their life is maintained stable, the machine tool will also be high temperature generated by the chip quickly discharged. Automotive gear processing along with machine tool design technology and tool coating and material technology continues to develop, for many countries in the gear dry cutting technology provides a rapid development of space, so as to achieve the continuous improvement of social benefits.

　　Hobbing dry cutting technology

　　In the early 1970s, Japan developed a carbide hob cylindrical gear dry cutting technology (Figure 1), and widely put on the market, such as Mitsubishi Heavy Industries and a company were processed out of carbide alloy gear equipment. 20 century 80's China's research tooling industry, gear processing plant, machine tool factories, materials research factory and many other units at the same time shoulder carbide alloy hob tools research and development tasks, and In this way began to hard alloy hob dry cutting technology to increase the use of some technologies and products have even won the scientific and technological achievements of the research awards, such as a reverse gear (m = 3.175), but due to a number of factors have not yet insisted on the research to go on. Currently such technology is used in synchronous processing gearboxes in small modulus, pinion gears and other products, in China did not achieve a strong promotion. Even if Japan is the first to introduce such technology has not been widely used, carbide hobbing tools are prone to chipping phenomenon, resulting in shortening the application cycle of the tool is not widely used in its production of the fundamental factors.

　　a. Comparison of hobbing and cutting for dry cutting hobbing.

　　Mitsubishi Heavy Industries in the development of dry cutting hob, in order to enhance the heat resistance of the tool, wear resistance of special coating treatment, the development of super dry cutting hob, in the m = 2.05, z = 49, β = 21.5 °, b = 40, etc., the workpiece cutting, select the 170HB, SCM415; the number of hobbing head for 3, that is, De = 75, the number of grooves need to be controlled in the 16, the cutting speed control is controlled in the 1 min / v = 200 m, the walking speed is controlled in the 1 min/v = 200 m, the cutting speed is controlled in the 1 min/v = 200 m, the cutting speed is controlled in the 1 min/v = 100 m. min/v=200 m, the rotating speed of the walking tool is controlled at 1 rpm=2.4 mm. Comparing the results of dry cutting and wet cutting of rotary smooth milling, it is found that the processing effect of dry cutting can be increased by 2 times compared with that of wet cutting, and the application cycle of the tool can be increased by 5 times, and the production cost of dry cutting will be decreased by more than 40% due to the lack of the use of cutting oil.

　　b. Dry Hobbing Machines.

　　Mitsubishi Heavy Industries in the GE hobbing machine special dry cutting technology research and development process, in the appropriate position of the machine cutting equipped with special chip conveyor, and compressed air will be used to the high temperature of the chip before contact with the machine quickly discharged, and therefore can prevent the hot chip caused by hot hobbing machine thermal deformation. Therefore, some hobbing gear pattern designed for horizontal, so as to facilitate the discharge of chips, such as Mitsubishi Heavy Industries GN hobbing machine, some industries have also launched a hobbing machine can be used in both wet and dry cutting technology. The dry cutting hobbing machine is shown in Figure 2.

　　

Gear Shaping Dry Cutting Technology

　　In the automotive gear processing technology, not only hobbing, but also gear extraction dry cutting technology, such as Tangze Iron Works, Mitsubishi Heavy Industries, etc. have successively developed a gear shaping machine, using dry cutting technology. Mitsubishi Heavy Industries processing gear shaper model SE25A, using dry cutting gear shaper material for high-speed steel, rough cutting speed is higher than the wet cutting speed of 1 ~ 2 times, the machining effect can be improved 1.3 ~ 1.5 times, tool life cycle can be extended by 3 ~ 5 times. When designing this kind of gear shaping machine, not only need to fully think about the machine chip removal and rigidity, but also use the equalisation axis to promote the reduction of noise and vibration of high-speed gear shaping.

　　Dry cutting technology for spiral bevel gears

　　a. Spiral Bevel Gear Cutting Machine for Powerful Dry Cutting.

　　The CNC of a company's six-axis fully controlled CNC hypoid gear milling machine has chosen a special spindle with high speed, and the rotational speed of the cutter spindle can be as fast as 1 min/2,000 r, which is impossible to achieve with a conventional shaking table gear cutting machine. The elimination of the complex gear chain ensures a balanced movement of the cutter spindle, thus avoiding the rise in spindle temperatures during high-speed cutting manoeuvres. The company needs to follow the relevant principles of aerodynamics, in the machining machine area mounted on a unique discharge device, the cutter head and the machining area into all the discharge cutting container, through the two high-pressure air nozzles will be blown to the back of the machine position of the baffle, so that it is far away from the tool and the workpiece, the machining of the production of the formation of 80 per cent of the heat along with the cutting of the simultaneous discharge of the machine to the outside of the front of the container needs to be turned sideways, so that to facilitate the replacement of the tool. The front face of the discharge container needs to be turned sideways to facilitate tool change. The spiral bevel gear is shown in Fig. 3.
　　b. Tooling for intensive dry cutting.

　　A newly developed PENTAC tool with a rod-shaped carbide tip was selected for force dry cutting. The carbide cutterhead is used in a company's 300CG type cutter grinding machine with diamond coated wheel cutting edges, and the cutterhead is made of carbide material, H10F type, which is equivalent to ISO grade K. The cutting surface of the cutterhead is made of TiA. The cutting surface of the cutter head is TiAIN coated.

　　c. Comparison of the economics of aggressive dry cutting.

　　A company compared the two types of cutting technology of 450HC gear cutting machine, and the results show that the strong dry cutting method can achieve good benefits compared with the traditional cutting technology, for example, the same cutting gear, the original cutting of each gear consumes 119.85 kW/min of electricity, while the strong dry cutting only requires 30.75 kW/min, equivalent to the original use 1/4. The machining time for large and small gears on the same cutting basis is about 1/3 to 1/2 of the conventional machining time when comparing Power Dry Cutting with conventional machining technology. although the use of coated hard alloy cutterheads in Power Dry Cutting technology tends to increase the cost, it is favourable to economic efficiency because of the extended cutterhead cycle, reduced cutter sharpening frequency and cutting oil saving, especially because of the cost reduction due to the improved production results, which can usually reduce the overall cost of gears by about 28%. The overall cost of gears can be reduced by about 28%.

　　III. Helical Gear Shaping Machines without Helical Gear Guides

　　Gear inserting machine in the straight gear or helical gear processing, need to use the guide to ensure that the cutting operation is carried out smoothly, insert helical gear should be on the spiral guide for reasonable use. The helix angle of the gear shaping cutter and the helix angle of the workpiece have equal requirements. And the spiral guide guide and gear knife guide put forward the same requirements, generally in the helical gear processing production, according to the requirements of the use of the spiral guide, the various types of helical gear processing, the need for reasonable replacement of the guide. But because the guide sleeve processing production process is very complex, and has a long manufacturing time, the guide sleeve replacement is very troublesome, so in the development of new products, helical gear insertion becomes a major obstacle to the development of new products, so you can change the structure of the helical gear insertion into two bodies, such as in the processing of the MSB Isuzu intermediate shaft to choose this type of method, the other method is to change the parameters of the helix angle of the workpiece under the basis of the existing guide sleeve in the design of the 1 252 the ring in the splitter, this method should be used, but all of the above approaches have constraints. For many years, therefore, it has been desirable to develop a machine tool for inserting helical gears without the use of helical guides.

　　

IV. Synchronised Gear Shaving Machine

　　In finishing gears, shaving is also one of the methods. In the shaving process, because the workpiece can be rotated under the drive of the shaving cutter, the two do not have a transmission chain, through the shaving cutter and the workpiece without lateral gap helical gears for the sub-meshing, the rate of the two contact points will be accompanied by a different direction of the gear processing tooth flanks along the shaving cutter to the tooth flanks, shaving cutter side of the existence of a number of small grooves, grooves and tooth flanks of the intersection of the line that is for the cutting edge, the gear flanks in its own sliding can be Gear side in its own slip can cut down the small chips. Shaving in the correction of shaving tooth shape, reduce tooth direction error and tooth roughness and other aspects of the effect is better, especially in improving the production effect of shaving, significantly lower than the cost of grinding, so far in the finishing gear is still widely used.

　　However, this type of shaving method still has shortcomings, because it belongs to the free drive, in reverse processing shaving rotation, easy to occur speed loss phenomenon, which has a direct impact on the ability to correct the tooth shape, especially in the radial correction of the wheel gear circle to produce a jump error, easy to be converted into tangential error, but also to let the tooth spacing error increases.

　　At present, foreign research and development of synchronous shaving machine, such as Mitsubishi Heavy Industries developed FS-type synchronous shaving machine. According to the company's introduction, this type of shaving machine tooth knife and workpiece there is a mandatory transmission chain, through the shaving shaft and workpiece shaft meshing drive synchronous control, not only can be corrected on the tooth shape and tooth direction, but also on the tooth pitch error and tooth ring runout to strengthen the corrections, and because of the shaving knife rotating in only one direction, without the need for reversal can be processed to complete the operation, can be made to reduce the processing time by 30%, to ensure that the effect of the shaving operation continues to improve.

　　In addition, the existing transmission shaving machine to open and switch between forward and reverse rotation, the formation of the acceleration and deceleration speed is easy to form a large load, resulting in razor wear and damage to the tooth surface of the workpiece, and synchronous shaving machine can completely avoid this problem. Some countries after research and development, after the test proved that synchronous shaving machine is easy to enhance the wear speed of the shaving cutter, but also make the roughness of the shaving surface becomes larger.

　　V. Application of gear grinding

　　Cylindrical gear grinding

　　In the finishing transmission cylindrical gears, the key link is grinding and shaving, but the roughness and accuracy of grinding gear flanks is significantly higher than shaving, especially the correction of thermal deformation. 20 century 80's, a company from the Japanese automobile manufacturing industry introduced the production of transmission technology, in the finishing gears began to widely use the grinding technology, since then, the processing of automotive gear enterprises began to Since then, the processing of automotive gear companies began to increase the introduction of gear grinding process, the current gear processing industry to produce a hot topic.

　　Limited to the current conditions, some manufacturers think that the production effect of the gear is not high, high cost investment will not promote a large number of automotive gear processing industry. But at present, along with the rapid development of NC gear grinding machine, grinding effect is gradually improved, the degree of correction of the gear is also more simple, CBN grinding wheel widely used, especially automotive enhancement of the precision requirements of the gear wheel and heavy motor vehicle transmissions in the core distance under the premise of the unchanged, in order to promote the gear strength continues to improve the increase in width of the gear surface, to enhance the precision of the teeth, the need to choose the gear grinding technology, therefore, through the heat after the grinding of teeth to replace the heat before the shaving processing technology is the inevitable choice. Therefore, it is inevitable to replace the pre-heat shaving processing technology by post-heat grinding.

　　Many countries will choose gear grinding for heavy-duty transmission gears and premium car transmissions, especially European countries will take gear grinding as a preferred technology for high-precision production of automotive gears. In recent years, China's transmission gears have been widely used grinding technology, which has improved the processing effect.

　　Spiral Bevel Gear Grinding

　　As the quality of automobile transmission is gradually improving, gear grinding is required for automobile spiral bevel gears and hypoid gears. In the past, foreign companies in the mechanical transmission bevel gear grinding machine production and processing, because of the relatively complex structure, high price, processing effect is not good, and did not use the grinding technology, the technology is only in the production of a number of small amount of high precision petroleum machinery, aerospace and precision machine tools, such as spiral bevel gears used in the enterprise.

　　

In recent years, along with the continuous development of CNC technology, the automotive processing industry has continued to develop similar grinding machines for use in the grinding of spiral bevel gears with rounded teeth. Some other industries have developed CNC series of circular bevel gear grinding machines and grinding technology, which promote the maximisation of the grinding effect. Circular arc tooth bevel gear single piece of grinding time has been equal to the cutting time, especially through the development of Waguli method of grinding forming spiral bevel gear processing, so that the automotive gear circular arc tooth bevel gear grinding technology in a large number of production enterprises to achieve a wide range of applications.

　　Sixth, the development of strong honing technology

　　60 ~ 70 years in the 20th century, the choice of disc-shaped or worm-shaped diffraction wheels as when the heat is repaired into the tooth surface of the finishing process, has been used in foreign automotive processing gear industry, there are still many processing gears in our country is using such technology, such as the author's business in the 60s began to introduce the British company produced disc-shaped honing wheel honing machine. Practice has proved that such technology can only be used in hardening the roughness of the gear tooth surface, and can not enhance the accuracy of the tooth shape and tooth direction, honing time is very long on the contrary, it will also make the gear precision is damaged, so this technology has not yet achieved widespread promotion. Although grinding can make the gear after heat precision, but according to the relevant foreign scholars of the experimental research shows that the gear surface ripples, that is, the ripple amplitude, wavelength and direction of several aspects will have an impact on the gear noise characteristics. Gear grinding to reduce noise is extremely unfavourable, there are many manufacturers in the completion of the grinding operation to choose the diffraction of teeth, which is likely to increase the manufacturing cost.

　　Seven, gear automatic sorting inspection machine

　　a. Inspection by gear pairing machine. In the pairing equipment can be used to mesh gears to high-speed operation, through the human senses audio-visual judgement of the gear inspection object with or without burrs and knocking noise.

　　b. Inspection with a gear double-sided mesh checker. The gear inspection and gear standard double-sided meshing at the same time, the gear to be inspected to the centre of the distance conversion changes, so as to judge whether there is a burr and knocking noise.

　　c. Manual visual inspection. Through manual visual inspection of the gear burr and bump noise. Although the above inspection methods have advantages and disadvantages, but there is still a common problem, that is, the configuration of special personnel to complete the operation, not only the higher cost and also need to rely on human sensory judgement, can not avoid unqualified transmissions assembly will let the gear burr and bump noise and disassembly again.

　　Eight, conclusion

　　This paper introduces new technologies in the automotive gear processing industry, including spiral bevel gear grinding machine dry cutting hobbing process, etc., China has a lot of units to carry out R & D work on such technologies, but there are still many new technologies in China in the blank, so China's manufacturers need to attach great importance to the new technologies and development trends, and promote China's automotive gear manufacturing level towards a new step.