The commonly used gear tooth profile is the involute tooth profile.
Classification： Blog
Release time：2024-06-20
If only the equal pitch is divided on the outer circumference of the friction wheel, the protrusions are installed, and then they mesh with each other to rotate, the following problems will occur:
The tangent point of the gear tooth produces sliding
The moving speed of the tangent point is fast and slow
Generate vibration and noise
Gear drive is both quiet and smooth, thus, the birth of the involute curve.
1) What is an involute
Wrap a string with a pencil tied at one end around the circumference of the cylinder, and then gradually release the string while the string is tight. At this point, the curve drawn by the pencil is the involute curve. The outer circumference of the cylinder is referred to as the base circle.
2) Example of an 8-tooth involute gear
After dividing the cylinder into 8 equal parts, tie 8 pencils and draw 8 involute curves. Then, wind the line in the opposite direction and draw 8 curves in the same way. This is a gear with an involute curve as the tooth shape and the number of teeth is 8.
3) Advantages of involute gears
Even if there is some error in the center distance, it can be meshed correctly;
It is easier to get the correct tooth shape, and it is easier to process;
Because of the rolling engagement on the curve, the rotary motion can be smoothly transmitted;
As long as the size of the teeth is the same, one tool can process gears with different numbers of teeth;
Tooth root stout, high strength.
4) Base circle and indexing circle
The base circle is the base circle that forms the involute tooth profile. The indexing circle is the reference circle that determines the size of the gear. The base circle and the indexing circle are important geometric dimensions of the gear. The involute tooth profile is a curve formed on the outside of the base circle. The pressure angle is zero degrees on the base circle.
5) meshing of involute gear
The indexing circles of two standard involute gears mesh tangentially at a standard center distance.
When the two wheels are meshed, it looks like two friction wheels (Friction wheels) with the diameter of the indexing circle d1 and d2 are driving. However, in practice, the meshing of involute gears depends on the base circle rather than the indexing circle.
The meshing contact points of the two gear tooth profiles move on the meshing line in the P1-P2-P3 order. Note the yellow teeth in the drive gear. A period of time after this tooth begins to engage, the gear is in two-tooth engagement (P1, P3). The meshing continues, and when the meshing point moves to point P2 on the indexing circle, only one meshing tooth remains. The meshing continues, and when the meshing point moves to the point P3, the next gear tooth starts to mesh at the point P1, and the two-tooth meshing state is formed again. As such, the two-tooth meshing and the single-tooth meshing of the gear wheel interactively transmit the rotational motion repeatedly.
The common tangent line A- B of the base circle is called a meshing line. The meshing points of the gears are all on this meshing line.
It is represented by an image diagram, as if the belt is cross-sleeved on the outer periphery of the two base circles to transmit power.
keyword： Gear,Shaft