Gear Structure classification
Generally, there are gear teeth, tooth grooves, end faces, normal faces, addendum circles, tooth root circles, base circles, and index circles
Gear teeth
Abbreviated as tooth, it is each convex part of the gear used for meshing. These convex parts are generally arranged in a radial pattern. The teeth on the mating gear contact each other, so that the gear can continuously mesh and run.
Cogging
It is the space between two adjacent gear teeth on the gear; the end face is on the cylindrical gear or cylindrical worm, and the plane perpendicular to the axis of the gear or worm.
End face
It is the plane at both ends of the gear.
Dharma
Refers to the plane perpendicular to the tooth line of the gear.
Addendum circle
Refers to the circle where the tip of the tooth is located.
Tooth root circle
Refers to the circle where the bottom of the groove is located.
Base circle
The generating line forming the involute is a purely rolling circle.
Index circle
It is the reference circle for calculating the geometric dimensions of the gear in the end face.
The main parameters
Number of teeth Z
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=20-40. Open (semi-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=17~20.
Helix angle
β> 0 is left-handed;
β <0 is right-handed
Tooth pitch
pn=ptcosβ (the subscripts n and t represent the marks of the normal direction and the end face respectively)
Modulus
Modulus refers to the ratio of the pitch p between two adjacent gear 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 modular gear teeth. For the moduli of straight, helical and conical gears, please refer to the standard modular series table (GB/T 1357-1987).
mn=mtcosβ
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
α rb=rcosα=1/2mzcosα
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 movement 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 standard gears is generally 20". In some occasions, α=14.5°, 15°, 22.50°, and 25° are also used.
Diameter of index circle
d=m*z
Center distance
a=1/2*m(z1+z2)
Correct meshing conditions
m1=m2,α1=α2,β1=β2
In order to prevent the gear from undercutting, for the standard straight-edge cylindrical gear with α=20°, z1≥17 should be taken. Z2=u·z1.
Addendum height coefficient and head clearance coefficient
—H*a, C*
When two gears mesh, the tooth tip of one gear always enters the tooth root of the other gear. In order to prevent thermal expansion from topping out and have space for lubricating oil, the tooth root height is required to be greater than the tooth tip height. For this reason, the addendum height coefficient and the head clearance coefficient are introduced.
Normal tooth: h*a =1; C*=0.25 Short tooth: h*a =0.8; C*=0.3
Luoyang Yujie Industry &Trade Co.Ltd located in Luoyang City, one of the main heavy industrial bases in China. We specialize in the production of bearings, nonstandard machinery parts, machine tools. For the bearings, we can offer cross roller bearing, slewing bearing, YRT bearing, thin section bearing, ball screw bearing, deep groove ball bearing, etc. For the nonstandard machine parts, we can produce gears, shafts, sprockets, molds, rollers, pulley, mining machine parts, etc as per customer drawing and requirements. For the machine tools, we offer CNC vertical machine center, CNC horizontal lathe, CNC gantry boring and milling machine, CNC floor type boring, and milling machine.
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