Gear tooth profile can be, the gear shape, tooth shape, tooth surface and manufacturing methods such as classification.
Gear tooth profile including tooth profile curve, pressure Angle, depth and deflection.Involute gear is relatively easy to manufacture, so the modern use of gear involute gear majority, with less cycloidal gear and circular-arc gear applications.
In the aspect of pressure Angle, the bearing capacity of small pressure Angle gear smaller;And pressure Angle of gear, though bearing capacity is higher, but under the same in the transmission torque of bearing the load increase, so only for special situations.And gear tooth depth has been standardized, generally adopt high standard tooth.The advantage of deflection gear is more, in all kinds of mechanical equipment.
In addition, the gear can also according to its shape can be divided into cylindrical gear, bevel gear, the non-circular gear, rack, worm, worm gear;According to the tooth line shape can be divided into straight gears, helical gears, herringbone gear, gear curve;According to the tooth's surface is divided into external gear and internal gear;According to the manufacturing method can be divided into casting rolling gear, gear, gear cutting, sintered gear, etc.
Gear manufacturing materials and heat treatment process on the gear bearing capacity and size weight has a great influence.Until the 1950 s, gear use carbon steel, the '60 s to switch to alloy steel, and multi-purpose surface hardened steel in the 70 s.According to the hardness, tooth surface can be divided into soft and hard tooth face two kinds of tooth surfaces.
Bearing capacity is low, soft tooth surface gear manufacturing more easily, but good running-in, more restrictions on the size and weight without strict for transmission, and a small amount in the production of general machinery.Because the gear pairs, relatively heavy burden on small wheels, so in order to make the working life of the gear is roughly equal size, small tooth surface hardness is higher than the big wheel.
Hard tooth surface gear of high bearing capacity, it is after the gear precision cutting, then quenching, surface hardening or carburizing and quenching treatment, in order to improve the hardness.But, in the heat treatment deformation of gear will inevitably produce, so after heat treatment must grind or fine cutting, grinding, to eliminate the error because of the deformation and improve the precision of gear.
Commonly used steel manufacturing gear quenched and tempered steel, hardened steel, carburizing and quenching steel and nitriding steel.Slightly lower than the strength of the cast steel forging steel, used to size the larger gear;Mechanical properties of gray cast iron is bad, can be used for the open gear transmission in light load;Nodular cast iron can partially replace steel manufacturing gear;Plastic gear is used for light load and more requirements of low noise, and its gear pairs, the thermal conductivity is commonly used in steel gears.
Future gear is overloaded, high speed, high precision and high efficiency, such as direction, and strive to small size, light weight, long service life and economic and reliable.
And gear theory and the development of the manufacturing process will be further study the mechanism for tooth damage, this is to establish a reliable basis for the strength calculation method, is to improve the gear bearing capacity and extend the life of the gear theoretical foundation;Development represented by circular arc tooth profile of the new tooth form;Study of new gear material and the new process to make gear;Study of the elastic deformation of gear, manufacturing and installation error and the distribution of temperature field, to carry on the modification of gear tooth, so as to improve gear running stability, and increase the contact area of tooth, when loaded with so as to improve the bearing capacity of the gear.
Friction and lubrication theory is a basic work in gear research and lubrication technology, research on elastic hydrodynamic pressure lubrication theory, promoting the synthetic lubricating oil and properly join extreme pressure additives in the oil, not only can improve the bearing capacity of tooth surface, and also can improve the transmission efficiency.