The forming surface of Coan cylindrical gear tooth profile surface is tangent to the base cylinder, and the forming line and axis form a βb Angle.

When Angle βb = 0, the tooth profile surface of the spur gear is formed.

Geometric parameters of cylindrical gears

The end tooth profile of the cylindrical gear is an exact involute, and the normal tooth profile is an involute, as shown in FIG. 8.27. Its end face is different from the normal plane parameter.

(1) The helix Angle on the base cylinder and the helix Angle on the indexing circle

(2) The normal surface modulus mn and the end surface modulus mt of the cylindrical gear

(3) Normal surface pressure Angle and end pressure Angle of cylindrical gear

(4) tip height coefficient and root high coefficient of helical gear

(5) The helix Angle on the base cylinder and the helix Angle on the indexing circle

(6) Correct meshing conditions for cylindrical gear transmission

The relationship between the modulus, pressure Angle and spiral Angle of a pair of cylindrical gears is

8.9.3 Equivalent gear of cylindrical gear

8.9.4 Contact degree of cylindrical gear transmission

The upper left is the meshing surface of spur gear drive, the lower left is the meshing surface of helical gear drive, B2B2 indicates the position where a pair of gear teeth enter meshing, B1B1 indicates the position where the gear teeth disengage.

8.9.5 Characteristics of cylindrical gear transmission

Advantages: 1) good meshing characteristics, 2) large contact degree, 3) the number of small teeth that do not produce root cuts is less than that of straight teeth.

Disadvantages: Axial force during operation.