Due to the need of use, the position relationship between the axes of a pair of spiral bevel gears is mainly as follows.
1. The two axes intersect vertically, and the intersection angle of the two axes is 90 °. The general spiral bevel gears use vertical intersecting axes, and the bevel gears with intersecting axes have no relative slip in the direction of tooth length.
2. Awhose axes intersect but not perpendicular, which can be at any angle. The vertical intersection axis is a special case of this kind of gear. Axis relationships that do not intersect vertically are rarely used.
3. Axis offset bevel gear, this kind of gear is equivalent to vertically intersecting pinion axis, upward or downward offset for a certain distance, this distance is called “offset”. Axis offset can make the wheel have a larger helix angle, which can reach about 50 °. Due to the increase of the helix angle of the small wheel, the end modulus of the small wheel is also increased, thus the diameter of the small wheel is increased, and the strength and life of the small wheel are improved. This kind of gear has relative sliding along the tooth length direction and the tooth height direction. Because the pitch surface of this kind of gear is part of the surface of a hyperbolic helicoid, it is customary to call this kind of gear “hyperbolic gear”, also known as “quasi-hyperbolic gear” or “quasi-hyperboloid gear”.