Due to the influence of manufacturing and installation errors, gear elastic deformation and thermal deformation, gear transmission will produce impact, vibration and eccentric load in the process of meshing, which will lead to early failure and transmission noise. Theoretical research and production practice show that it is not enough to only improve the manufacturing and installation accuracy of gears to meet the high performance requirements of gears, and will greatly increase the manufacturing cost of gear transmission. The proper modification of the tooth profile and direction of the involute cylindrical gear has obvious effect on improving its operation performance, increasing its bearing capacity, prolonging its service life and reducing the noise of the transmission system.
Gear modification generally includes two parts: tooth profile modification and tooth direction modification.
Tooth profile modification is to cut a part of the tooth surface that may interfere with a pair of ideal meshing teeth along the direction of tooth height. Generally, the part to be cut is at the top and root of the tooth. The modified tooth profile is called “K-shaped tooth”. Tooth profile modification is to modify the helix of the tooth surface according to the predetermined law to obtain a more uniform load distribution in the tooth direction. Generally, the tooth thickness direction is modified as the middle high (thick), and the two ends are low (thin), which is called “drum shaped tooth”; there are also trimmed as one end high and one end low, which is called “taper tooth”.
Gear shaping technology has been used for a long time in foreign gear industry, and it is also widely used in domestic automobile gear. The application of tractor gear shaping technology in China is still in its infancy.
For low-speed and low-power tractor gears, there is no need for precise shape modification, and no shape modification or simple shape modification can meet the product requirements. However, for high-speed and high-power tractors, gear shaping technology must be used, especially for power shift transmission gears, which must be precise, and at the same time, the tooth profile and tooth direction must be modified to meet the use requirements.
With the development of people’s material and cultural needs and manufacturing technology, people have higher and higher requirements for the performance of various products, and users have higher and higher requirements for the noise, operation convenience and comfort of the tractor gearbox. It is necessary for the development of the market to modify the transmission gears of the tractor. But if we break away from the requirements of products and blindly pursue high performance and over shape the gears, we can not achieve good results. According to different products, different gear shaping methods are adopted to meet the needs of different grades in an economic and effective way, so as to achieve the best shaping effect and the best economic benefit.