Gear is a mechanical parts that can mesh.It is extremely widely used in mechanical transmission and the entire mechanical field.As early as 350 BC, Aristotle, a famous philosopher in ancient Greece, recorded gears in the literature.So, what are the classification of gears?What are the basic terms and size calculations of gears?Lets take a look today.
Classification of gear
There are many types of gears, and their classification methods are most commonly based on gear axis.It is generally divided into three types: parallel axis, intersection shaft and staggered shaft.
1) Parallel axis gear: Including positive gears, oblique gears, inner gears, gradia and diagonal shifts.
2) intersect a shaft gear: there are straight tooth cone gear, arc tooth cone gear, zero -tooth cone gear, etc.
3) Interlaced axis gear: There are staggered shaft oblique gear, worm worm wheels, quasi -dual -curved gears, etc.
Basic term and size calculation of gear
Gear has a lot of terminology and expression methods unique to gears. In order to enable everyone to understand the gears more, here are some basic terminology that are often used.
1) Names of each part of the gear
2) The term of the size of the wheel teeth is a model
M1, M3, M8 ... It is called Model 1, Model 3, Model 8.The number of molds is a common name in the world. The use of symbol m (modulus) and numbers (millimeters "to indicate the size of the wheel teeth. The larger the number, the larger the wheel teeth.
In addition, in countries (such as the United States) using British -made units (such as the United States), the size of the wheel teeth is used to use the symbol (diameter) and numbers (the number of gears when the diameter of the division round is 1 inch).For example: DP24, DP8, etc.There are also special titles that use symbols (weeks) and numbers (millimeters) to represent the size of wheel teeth, such as CP5 and CP10.
Models can get the tooth distance (P) by the perians, and the length of the tooth distance is the length between the two teeth.
Use formula to represent:
Comparison of wheel teeth of different modular numbers:
3) Pressure angle
Pressure angle is a parameter that determines gear tooth shapes.That is the tilt of the wheel tooth surface.Pressure angle (α) is generally 20 °.In the past, gears with a pressure angle of 14.5 ° were very popular.
The pressure angle is a point between the tooth surface (generally refers to the node), the angle between the radius line and the cut line of the tooth shape.As shown in the figure, α is the pressure angle.Because α = α, α is also a pressure angle.
When the meshing state of A tooth and B tooth looks from the node:
A tooth promotes point B on the node.At this time, the driving force is on the common method of A tooth and B tooth.In other words, the common method line is the direction of force, and the direction of pressure, and α is the pressure angle.
Model (m), pressure angle (α) plus the number of teeth (Z) is the three basic parameters of the gear. Based on this parameter, calculate the size of each part of the gear.
4) High teeth and thick teeth
The height of the wheel teeth is determined by the mold (M).
The height of the top (HA) is the height from the top of the tooth to the division line.ha = 1m.
The height of the teeth (HF) is the height from the root of the teeth to the division line.hf = 1.25m.
The benchmark of teeth thickness (s) is half of the teeth distance.s = πm/2.
5) The diameter of the gear
The parameter of the gear size is the division of the gear (d).With the degree of division round, the teeth distance, thickness, high teeth, high tooth top, and height of the teeth can be determined.
The division circle cannot be seen directly in the actual gear, because the division circle is a circle that assumes the size of the gear.
6) Central distance and gap
When a pair of gears are cut into mesh, the central distance is half of the sum of two differential circular diameters.
In the meshing of the gear, to get a smooth meshing effect, the gap is an important factor.The gap is the gap between the tooth surface when the gear mesh.
There are also gaps in the high direction of the gear.This gap is called a cleaance.The top gap (C) is the difference between the height of the gear to the top of the gear.
7) Slip tooth gear
The gears that are turned on the wheels of the gear tooth to the oblique gear are twisted.Most of the geometric geometric gauge can be applied to the oblique gear.There are 2 ways of oblique tooth gear, according to their reference surfaces:
Facial (axis straight angle) benchmark (end -faced mold/pressure angle "
Dharma (tooth straight angle) benchmark (method directional number/pressure angle "
The relationship between the end fabric modulus MT and the method of the modulus MN mt = mn/cosβ

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