1. Number of teeth Z: The closed gear transmission generally has a high speed. In order to improve the stability of the transmission and reduce the impact and vibration, it is better to have more teeth than a smaller number of teeth. The number of teeth of the pinion can be taken as z1=20~40. For open (semi-open) gear transmission, since the gear teeth are mainly worn out, in order to prevent the gear from being too small, the pinion may not use too many teeth, generally z1=17~20. In order to prevent the gear from undercutting, for the standard support cylindrical gear with α=20o, z1≥17 should be taken. Z2=u·z1.
2. Pressure angle α rb=rcosα=1/2mzcosα: at the tangent point P of the pitch circles of the two gears, the common normal of the two tooth profile curves (that is, the force direction of the tooth profile) and the common tangent of the two pitch circles (that is, P The acute angle contained by the instantaneous direction of motion at the point) is called the pressure angle, also known as the meshing angle. For a single gear, it is the tooth form angle. The pressure angle of the standard gear is generally 20”. In some occasions, α=14.5°, 15°, 22.50° and 25° are also used.
3. Module m=p/π: The index circle of the gear is the benchmark for designing and calculating the size of each part of the gear, and the circumference of the gear index circle=πd=z p The modulus m is a basic parameter that determines the size of the gear. The gear with the same number of teeth has a large module, and its size is also large.
4. Tooth top height coefficient and top clearance coefficient—h*a, C*: When two gears are meshed, the tooth top of one gear always enters the tooth root of the other gear. space, the tooth root height is required to be greater than the tooth tip height. The addendum height factor and the tip clearance factor are introduced for the second time. Normal teeth: h*a =1; C*=0.25 Short teeth: h*a =0.8; C*=0.3 When machining mechanical parts, we should understand the different characteristics and requirements of different parts in order to process high-quality Hardware accessories and different types of machine tool accessories.
Looking forward to your consultation if there is anything unclear