In the world of transmission, the sector of bevel gear occupies a special place.
In this article we want to give an overview of bevel gears, in particular spiral bevel gears; to establish solid foundations in order to allow a better understanding of referrals.
Within a pair of gears, with a ratio different from 1: 1, the pinion is defined as the gear with the fewest number of teeth and crowns the gear with the greatest number of teeth.
The conical wheels perform the function of distributing the motion, usually at 90 °, but it is possible to distribute the motion even with different angles.
Bevel gears are divided into several types; the first distinguishing factor is the type of teeth:
- Straight teeth
- Spiral teeth
The type most commonly used is the spiral tooth type.
Spiral tooth gears distribute the load over more teeth than the straight tooth gears, making them less noisy and thus being able to carry a greater torque for the same size.
Another parameter is the arrangement of the gear axes; those so far treated (image 1) have the axes intersecting belonging to the same plane, the hypoid gears have the axes of the gears on different planes. (images 2-3)
This difference entails a greater coverage and a greater gradualness of the transmission; with the same ratio, the hypoid pinion will have a larger size and therefore a greater load capacity.