Number of teeth Z
Spiral bevel gear
Spiral bevel gear
Closed gear transmission generally has a higher speed. In order to improve the stability of the transmission and reduce the impact and vibration, it is better to have more teeth. The number of teeth of the pinion can be z1=2040. Open (half-open) gear transmission, because the gear teeth are mainly worn out, in order to prevent the gear from being too small, too many teeth should not be used for the pinion, generally z1=1720.
Helix angle
β> 0 is left-handed;
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Tooth pitch
pn=ptcos (the subscripts n and t represent the marks of the normal direction and the end face respectively)
Modulus
The modulus refers to the ratio of the pitch p between the two adjacent teeth on the same side tooth profile to the circumference ratio π (m=p/π), in millimeters. Modulus is one of the most basic parameters of modulus gear teeth. The modulus of straight, helical and conical gears can all refer to the standard modulus series table (GB/T 1357-1987).
mn=mtcos
m=p/ π
The index circle of the gear is the basis for designing and calculating the size of each part of the gear, and the circumference of the index circle of the gear=πd=z p
The modulus m is a basic parameter that determines the size of the gear. A gear with the same number of teeth has a larger module, and its size is also larger.
pressure angle
rb=rcos =1/2mzcos
At the tangent point P of the pitch circles of the two gears, the acute angle between the common normal line of the two tooth profile curves (ie the force direction of the tooth profile) and the common tangent line of the two pitch circles (ie the instantaneous direction of motion at point P) is called The pressure angle is also called the engagement angle. For a single gear, it is the tooth profile angle. The pressure angle of a standard gear is generally 20". In some occasions, =14.5 degree , 15 degree , 22.50 degree , and 25 degree are also used.
Diameter of index circle
d=mz
Center distance
a=1/2m(z1 plus z2)
Correct meshing conditions
m1=m2, 1= 2, 1= 2
In order to prevent the gear from undercutting, for the standard straight-edge cylindrical gear with =20o, z1 Greater than or equal to 17 should be taken. Z2=u·z1.
Addendum height coefficient and head clearance coefficient
—Ha, C
When two gears are meshed, the tooth tip of one gear always enters the tooth root of the other gear. In order to prevent thermal expansion from topping and to have space for lubricating oil, the height of the tooth root is required to be greater than the height of the tooth tip. For this reason, the addendum height coefficient and the head clearance coefficient are introduced.
Normal tooth: ha =1; C=0.25 Short tooth: ha =0.8; C=0.3
