What is gear efficiency?
Gear efficiency can be expressed as the ratio (expressed as a percentage) of the power from the input shaft to the power from the output shaft in a gear pair.
When classifying gears by focusing on the positional relationship between the two axes of a gear pair, gears are classified into parallel axis gears (spur gears, gear racks, internal gears, helical gears, helical gear racks, double helical gears), intersecting axis gears (straight bevel gears, spiral bevel gears, zerol bevel gears) and nonparallel and nonintersecting axis gears (screw gears, worm gears).
The general efficiency of each type of gear (excluding bearing loss, loss of lubricating oil agitation, etc.) is as follows.
Parallel axis gears ... 98.0 - 99.5%
Intersecting axis gears ... 98.0 - 99.0%
Nonparallel and nonintersecting axis gears (screw gears) ... 70.0 - 95.0%
Nonparallel and nonintersecting axis gears (worm gears) ... 30.0 - 90.0%
The meshing of parallel axis gears and intersecting axis gears is almost entirely due to "rolling," and the relative "slippage" is very small, resulting in high efficiency.
On the other hand, the rotation and power transmission of the nonparallel and nonintersecting axis gears is due to relative slippage, so the effect of friction is large, and the efficiency is low.