On the surface, it could seem that gears are being “reduced” in quantity or size, which is partially true. When a rotary machine such as an engine or electrical motor needs the result speed decreased and/or torque increased, gears are commonly used to accomplish the required result. Gear “reduction” particularly refers to the speed of the rotary machine; the rotational speed of the rotary machine can be “decreased” by dividing it by a gear ratio greater than 1:1. A gear ratio greater than 1:1 is certainly achieved whenever a smaller equipment (decreased size) with fewer amount of tooth meshes and drives a more substantial gear with greater amount of teeth.
Gear reduction has the opposite influence on torque. The rotary machine’s result torque is improved by multiplying the torque by the apparatus ratio, less some performance losses.
While in lots of applications gear reduction reduces speed and boosts torque, in other applications gear reduction is used to improve acceleration and reduce torque. Generators in wind turbines use gear decrease in this fashion to convert a comparatively slow turbine blade speed to a higher speed capable of producing electricity. These applications make use of gearboxes that are assembled reverse of those in applications that reduce rate and increase torque.
How is gear reduction achieved? Many reducer types are capable of attaining gear reduction including, but not limited to, parallel shaft, planetary and right-position worm gearboxes. In parallel shaft gearboxes (or reducers), a pinion gear with a specific number of the teeth meshes and drives a more substantial gear with a greater number of teeth. The “decrease” or gear ratio is calculated by dividing the number of tooth on the large gear by the amount of teeth on the tiny gear. For instance, if an electric motor drives a 13-tooth pinion gear that meshes with a 65-tooth equipment, a reduced amount of 5:1 can be achieved (65 / 13 = 5). If the electric motor speed is definitely 3,450 rpm, the gearbox reduces this speed by five occasions to 690 rpm. If the engine torque can be 10 lb-in, the gearbox boosts this torque by a factor of five to 50 lb-in (before subtracting out gearbox efficiency losses).
Parallel shaft gearboxes many times contain multiple gear sets thereby increasing the gear reduction. The full total gear decrease (ratio) depends upon multiplying each individual gear ratio from each equipment established stage. If a gearbox includes 3:1, 4:1 and 5:1 gear sets, the total ratio is 60:1 (3 x 4 x 5 = 60). Inside our example above, the 3,450 rpm electric engine would have its quickness decreased to 57.5 rpm by using a 60:1 gearbox. The 10 lb-in electric motor torque would be risen to 600 lb-in (before effectiveness losses).
If a pinion gear and its mating equipment have the same number of teeth, no reduction occurs and the gear ratio is 1:1. The gear is named an idler and its own primary function is to improve the path of rotation rather than reduce the speed or increase the torque.
Calculating the apparatus ratio in a planetary equipment reducer is less intuitive as it is dependent on the amount of teeth of the sun and ring gears. The earth gears act as idlers and don’t affect the apparatus ratio. The planetary equipment ratio equals the sum of the amount of teeth on sunlight and ring gear divided by the amount of teeth on sunlight gear. For instance, a planetary set with a 12-tooth sun gear and 72-tooth ring gear includes a gear ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear pieces can achieve ratios from about 3:1 to about 11:1. If more equipment reduction is necessary, additional planetary stages may be used.
The gear decrease in a right-angle worm drive is dependent on the number of threads or “starts” on the worm and the number of teeth on the mating worm wheel. If the worm has two starts and the mating worm wheel offers 50 teeth, the resulting gear ratio is 25:1 (50 / 2 = 25).
When a rotary machine such as for example an engine or electric motor cannot supply the desired output velocity or torque, a gear reducer may provide a good solution. Parallel shaft, planetary, right-angle worm drives are normal gearbox types for achieving gear reduction.