Some concept about gears
The gear is a toothed wheel, and its meshing action transmits the rotation of one shaft to other shafts, and transmits motion or torque between the two shafts. There are many types of gears. According to the axiality of the gears, there are parallel axis, intersecting axis, and non-parallel and non-intersecting axis.
Modulus: a pointer indicating the size of a gear. The modulus of a pair of engaged gears must be the same. Otherwise, the two gears have different tooth specifications and cannot run smoothly. The modulus can be defined as: the ratio of the pitch diameter and the number of teeth, the unit is usually (mm), the modulus is usually used in the metric system. and in the inch system, the same position is the diameter pitch, that is, the number of gear teeth and pitch and diameter The ratio of is in the sense the reciprocal of the modulus. The unit is (teeth / inch). Modulus: m = D / N Diameter section: Pd = N / D
Pitch circle: It is a theoretical circle. In a pair of meshed gears, the pitch circle must be tangent to each other
Pitch diameter: is the diameter of the pitch circle, D
Pressure line: When the two gears are in contact, the direction perpendicular to the contact surface is that, usually the forward load is transmitted along the direction of the pressure line.
Pressure angle PA: This is the angle between the common tangent of the two gear pitch circles and the pressure line. The general pressure angles are 14.5 degrees and 20 degrees. Today, more than 20 pressure angles are used to prevent interference.