Explanation of force analysis of straight and helical cylindrical gears

The force analysis of the gear is the basis for the design of the gear, and it can also provide initial conditions for the design of shafts and bearings.When the gear is meshed, it can be regarded as the contact of two cylinders. Its radius is equal to the radius of curvature of the two tooth profiles at the meshing point. The meshing point moves from the tooth root to the tooth tip (drive wheel). Fatigue damage mostly occurs near the node, and Generally, only a pair of gear teeth are loaded near the nodes, so the force analysis is calculated when the nodes are meshed.

A pairgearThe state of force at first contact is an important basis for strength calculation.The stress concentration of the tooth root is the source of fatigue cracks, so the tooth root fillet should not be too small; the side of the tooth root subjected to tensile stress is more suitable to be broken.

The position of the dangerous section of the tooth root is determined by the 30° tangent method.Two straight lines that form a 30° angle with the symmetrical centerline of the gear tooth are tangent to the transition curve of the tooth root fillet, and the tooth thickness connecting the two tangent points is the tooth thickness of the dangerous section of the tooth root.

XNUMX. Explanation of force analysis of spur gear

1. The size of each force

2. The direction of each force

3. Correspondence of each force

XNUMX. Explanation of force analysis of helical cylindrical gear

1. The size of each force

2. The direction of each force

3. Correspondence of each force

Three, gear force analysis

In the force analysis of gear transmission, it is necessary to distinguish the driving wheel and the driven wheel.Regarding the magnitude of each force, the calculation formula has been given. The following will focus on how to correctly judge the direction of each force and how to correctly label it in the figure for discussion:

1. Circumferential force:

2. Radial force:

3. Axial force:

4,Cylindrical gearThe judgment method of each component force direction of spur bevel gear transmission can be summarized as follows:

5. The marking method of each component force direction of helical cylindrical gear and straight bevel gear transmission is shown in the following figure: