What is a Bevel Gear?

Bevel gears are used to transmit motion and power between two intersecting axes. In general machinery, the angle of intersection between the two axes of the bevel gear is equal to 90 ° (but it may not be equal to 90 °). Similar to cylindrical gears, bevel gears have an indexing cone, a tip cone, a root cone, and a base cone. The cone has a large end and a small end, and the circles corresponding to the large end are called an index circle (with a radius of r), a tooth top circle, a tooth root circle, and a base circle. The movement of a pair of bevel gears is equivalent to a pair of pitch cones making pure rolling ^[1] .

The following figure shows a pair of special bevel gear drives. Where the number of teeth of wheel 1 is

, The indexing circle radius is

, The reference cone angle is

; The number of teeth of wheel 2 is

, The indexing circle radius is

, Indexing cone angle

= 90 °, its indexing cone surface is a plane, this gear is called crown gear.

Similar to a spur gear, with a nominal normal load

Decomposed at the average indexing circle of the pinion into

The bevel gear takes the big end parameter as the standard value, so when calculating its geometric size, it should also take the big end as the standard. As shown in the figure below, the graduation circle diameters of the two bevel gears are

In the formula, R is the distance from the top of the indexing cone to the big end, which is the cone distance.

,

The indexing cone angle of the two bevel gears (referred to as the indexing cone angle).

Geometry of bevel gear drive

The transmission ratio of the two wheels is

When the axis angle between two bevel gears

= 90 °, when

= 90 ° The above formula becomes

When designing bevel gear transmission, it can be based on a given transmission ratio

, According to the above formula, determine the value of the two-way taper angle.

As for the size of the cone angle of the bevel gear tip and the cone angle of the tooth root, it is related to the requirements of the top clearance of the two bevel gears when they are meshed. According to national standards (GB / T 12369-1990, GB / T12370-1990), equal top clearance bevel gear transmission is now used, and the top clearance of the two wheels is equal from the large end to the small end of the gear. The cones of the degree cone and the root cone coincide at one point. However, since the two-wheeled tooth top cones are parallel to the tooth root cone of the other bevel gear that meshes with it, their cones no longer coincide with the indexing cone cones. This bevel gear is equivalent to reducing the tooth tip height of the small end of the gear tooth, thereby reducing the possibility of the tip of the tooth tip being too sharp; and the larger radius of the tooth root fillet is conducive to improving the bearing capacity, tool life and storage Oil lubrication ^[3] .

Geometric parameters and dimensions of standard bevel gear transmission (

= 90 °)

name	Code	gear	big gear
Taper angle
Tooth height
Root height
Indexing circle diameter
Tooth circle diameter
Tooth root diameter
Cone distance
Tooth root angle
Cone angle
Root cone angle
Head gap		(general )
Indexing tooth thickness
Equivalent number of teeth
Tooth width		(Rounding)