When the output speed, torque, and geometric position of the output shaft of the power machine are not compatible with the requirements of working equipment, a gear transmission can use to connect them to meet the different needs of different working conditions. The comprehensive technical and reasonable index is the most fundamental factor that choosing gear transmission schemes, especially in high power transmission. For relatively small power transmission, based on the condition that meetings the working performance, it is suitable to choose transmission equipment with simple structure and low cost. For relatively large power transmission, it is reasonable to give priority to the efficiency of gear transmission to save energy, reduce operation, and maintenance fees. Also, the selection of gear transmission equipment should be compatible with the level of design and manufacture.
Gear Transmission Feature
The feature of gear transmission is to take advantage of the meshing of gear teeth of the two gear to transmit power and motion. According to the relative position of gear axis, there are parallel shaft cylindrical gear transmission, intersecting shaft bevel gear transmission, and interleaved shaft spiral gear transmission. They are compact structure, high efficiency, long life.
Gear Transmission Type
1. Cylindrical gear transmission
It uses in the parallel shaft, the transmission ratio can reach 8 in a single stage, up to 20. 45 in two-stage, up to 60. 200 in three-stage, up to 300. the transmission power can reach up to 10 0,000 kilowatts, the rotation speed can reach up to 100,000 rpm/minute, and the peripheral speed can be 300 meters/second. The efficiency of the single-stage is 0.96-0.99. The gear transmission is suitable in the medium and low-speed conditions. The operation of helical gear is smooth, which applies to the medium and high-speed state. Double helical gear transmission is suitable for high power and high torque transmission. The meshing form of cylindrical gear is: external gear transmission, which is meshed by two external gears, and the steering direction of the two is the opposite. Internal gear transmission, which is meshed by an internal and a small external gear, and the steering direction of the two is the same. The gear and rack transmission, which can change the rotation of gear into the linear movement of the rack, or vice versa.
2. Bevel Gear Transmission
It is used in the intersecting shaft. The transmission ratio of the single-stage can reach up to 6, the maximum is 8. The transmission efficiency is 0.94-0.98. The power of straight bevel gear can reach up to 370 kilowatts, and peripheral speed is 5 meters/second. The operation of helical bevel gear is smooth, and gear load capacity is very high, but the manufacturing technology is very hard. Curved-tooth bevel gear runs smoothly. the transmission power can reach up to 3700 kilowatts, the peripheral speed can reach up to 40 meters/second.
3. hyperboloid gear
It is used in the intersecting shaft. The transmission ratio of the single-stage is 10, the maximum reaches 100. The transmission power can reach up to 750 kilowatts, the transmission efficiency is 0.9-0.98, the peripheral speed can reach up to 30 meters/second. Because of the axis offset, the installation of pinion cantilever can avoid. It is widely used in the automotive and tractor.
4. Spiral Gear Transmission
It is used in the intersecting shaft, the transmission ratio can reach up to 5. The load capacity is relatively low, the wear is severe but the application is small. The sliding between the tooth surfaces of the worm is large, the heat is more, the transmission efficiency is low, which is 0.45-0.97.
5. Worm Transmission
The main type of intersecting shaft, the axis stagger angle is generally 90 degrees. The worm transmission can achieve a high transmission ratio. Usually, the single-phase is 8-80, and can reach up to 1500; The transmission power can reach up to 4500 kilowatts; the speed of worm can reach up to 30,000 rpm; the peripheral speed can reach up to 70 meters/second. The transmission of the worm is smooth, the transmission ratio is precise and can be self-locking, but the transmission efficiency is lower than 0.5.
6. ARC Gear Transmission
It takes advantage of convex and concave arc to be the gear transmission of the tooth profile. The two tooth profiles are in point contact. In the process of meshing, the contact point moves along the axis direction, the continuous transmission is got by the longitudinal coincidence whose value is greater than 1. The feature is high contact strength and load capacity and is easy to form oil film, no undercutting phenomenon, the wear of gear surface is even, the running performance is good. But it is sensitive to the central distance, cutting gear depth and error of spiral angle. So the requirements for manufacture and installation are very high.
7. Cycloidal Gear Transmission
Using the cycloid to be gear transmission of the gear tooth. The contact stress force between transmission tooth surface is small, the wear resistance is good, no undercutting phenomenon. But the requirement of the precision of manufacturing is very high and is sensitive to the central distance. It is only used in the watch and meters.
8. Planetary Gear Transmission
There are many types of a planetary gear and the performance of different types is different. it is important to choose suitable types based on the working conditions. The most used is the common planetary gear transmission that consists of the sun gear, planet gear, internal gear and planet carrier, cycloidal pinion transmission, and harmonic transmission, etc.
The planetary gear transmission usually is composed of parallel shaft gear, which is the small size, lightweight, and the output shaft and the input shaft is in the same line.
The Noise Control of Gear Transmission
Although the right use and maintenance of gear transmission can’t reduce the level of system noise, ensure the transmission accuracy, yet it can prevent the deterioration of index and increase service life.
1. Internal cleaning of the transmission system
Any impurities which enter the internal will affect and destroy the gear transmission system, results in noise and destroys the transmission system.
2. The working temperature of the normal working of the system
Ensuring the working temperature of the normal working of the system, preventing the system from being deformed due to excessive temperature rise, can prevent the increase of noise.
3. Lubrication in time and proper use of oil
Careless lubrication and wrong use of grease will have incalculable damage to the system. Ensuring the lubrication of the system in time can control the noise in a certain range, and delay the trend of deterioration. The gear at high speed, which will produce huge heat due to the friction of the tooth surface, will cause the damage of the tooth due to improper lubrication. In the process of design, the gear pair should have proper backlash. The right use and selection of grease can ensure the normal operation of the system and stabilize the noise level.
4. The right use of gear motion system
Based on the normal operating order of the system, the system can avoid damage and ensure the noise level of stabilization. The use of the system should be in the normal load range because the transmission noise of the gear transmission system will increase as the load increases.
5. Regular maintenance and repair
Regular maintenance and repair(oil change, replace worn parts, fastener loose parts, verify geometric precision) can improve the system to resist the noise level and maintain the stability of the system.
