Views: 1 Author: Site Editor Publish Time: 2022-03-28 Origin: Site
Gear is the core transmission component in automobile movement, and its processing quality has a direct impact on the vibration and noise of automobile assembly and the reliability of the whole vehicle, and sometimes becomes the key factor restricting the improvement of product level.
Classification of gear
It can be divided into four categories.
1) Cylindrical gear.
According to the structure of parts can be divided into disk teeth and shaft teeth, according to the tooth shape can be divided into straight teeth and helical teeth, used for the transmission of parallel axis power and motion, such as gearbox speed transformation, engine ignition timing, etc..
2) Bevel gear.
According to the tooth shape can be divided into straight bevel gear and spiral bevel gear, used for cross shaft or staggered shaft power and motion transmission, such as rear axle differential and reducer. Among them, spiral bevel gear, according to the difference of tooth shape processing principle and method, has formed different system system in the world, usually called system. Chinese automobile industry basically adopts arc taper tooth (also known as Gleason system) or cycloid isometric tooth (also known as Oricon system).
For example, the sliding gear sleeve used for variable speed connection and the gear ring used for planetary variable speed transmission belong to the inner gear ring, and the synchronous gear ring used for variable speed synchronous control belongs to the outer gear ring.
4) Special purpose gear.
Such as oil pump gear, speed gauge worm, steering rack and so on.
Automotive gear generally belongs to mass specialized production, cylindrical gear and bevel gear have a wide range of representative, according to different structure and accuracy needs to use different process combination. Due to the high investment in equipment, the selection of process methods usually takes full account of available resources.
The control of micro deformation and process stability in gear machining is relatively complicated.
Isothermal normalizing is used to obtain good processing performance and uniform metallographic structure with tendency deformation. For low speed mesh gear with low precision, the gear can be heated before shaving and no longer processed after heating. The application of radial shaving method expands the range of gear shaving. There are two ways of hot processing of cylindrical gear: honing and grinding. The cost of honing is low but the ability of tooth shape correction is weak, and the grinding precision is high but the cost is high. It has been widely concerned that the tooth tip modification along the tooth height direction and drum tooth modification along the tooth length direction can significantly reduce the meshing noise and improve the transmission performance.
The involute tooth shape is the most common. There are two kinds of commonly used machining methods for involute tooth shape, namely forming method and developing method.
The following are several tooth shape processing methods：
1) Milling tooth
Using disk mold milling cutter or finger milling cutter milling teeth belong to the forming method processing, milling cutter tooth section shape and gear tooth shape corresponding. This method has low processing efficiency and accuracy and is only suitable for single piece and small batch production.
2) Forming grinding
Also belongs to the forming process, because the grinding wheel is not easy to dress, use less.
3) Gear hobbing
It belongs to developing process and its working principle is equivalent to meshing of a pair of helical gears. The prototype of gear hob is a helical gear with a large helical Angle. Due to the small number of teeth (usually z = 1), the teeth are very long and form a worm with a small helical Angle around the shaft. After slotting and shoveling, it becomes a hob with cutting edge and back Angle.
Shaving is a common finishing method for non - hardened tooth surfaces in mass production. Its working principle is to use the gear shaver and the machined gear for free meshing motion, with the help of the relative slip between the two, shaving from the tooth surface very fine chips, in order to improve the accuracy of the tooth surface. Shaving can also form drum teeth to improve the contact area of tooth surface.
5) Gear shaper
In addition to hobbing, gear shaper is a common gear cutting process using development method. Gear shaper, gear shaper cutter and workpiece equivalent to a pair of cylindrical gear meshing. The reciprocating motion of the gear shaper is the main motion of the gear shaper, while the circular motion of the gear shaper is the feed motion of the gear shaper.
6) Expansion grinding method
It is a kind of tooth shape finishing method, especially for hardened gears, which is often the only finishing method. Expansion grinding wheel can be used for worm grinding wheel, conical grinding wheel or disc grinding wheel.
7) Gear honing
The honing principle is similar to gear shaving. The honing wheel and the workpiece are similar to a pair of helical gears engaged without backlash. The relative sliding of the meshing place is used to apply a certain pressure between the tooth surfaces to carry out the honing.
8) Electric spark wire cutting
It is developed on the basis of edM perforation and forming. It has not only developed the application of edM, but also replaced edM perforation and forming in some aspects.