On the surface, it could seem that gears are being “reduced” in quantity or size, which is partially true. Whenever a rotary machine such as for example an engine or electric motor needs the result speed reduced and/or torque improved, gears are commonly utilized to accomplish the desired result. Gear “reduction” specifically refers to the acceleration 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 higher than 1:1 is certainly achieved whenever a smaller equipment (reduced size) with fewer number of teeth meshes and drives a more substantial gear with greater amount of teeth.
Gear reduction gets the opposite influence on torque. The rotary machine’s result torque is increased by multiplying the torque by the gear ratio, less some effectiveness losses.
While in many applications gear reduction reduces speed and raises torque, in various other applications gear decrease is used to improve swiftness and reduce torque. Generators in wind turbines use gear reduction in this manner to convert a comparatively slow turbine blade acceleration to a higher speed capable of generating electricity. These applications make use of gearboxes that are assembled opposing of these in applications that decrease acceleration and increase torque.
How is gear decrease achieved? Many reducer types are capable of attaining gear reduction including, but not limited by, parallel shaft, planetary and right-angle worm gearboxes. In parallel shaft gearboxes (or reducers), a pinion gear with a specific number of teeth meshes and drives a more substantial gear with a greater number of teeth. The “decrease” or gear ratio can be calculated by dividing the amount of the teeth on the large gear by the amount of teeth on the small gear. For instance, if an electric motor drives a 13-tooth pinion gear that meshes with a 65-tooth gear, a reduction of 5:1 can be achieved (65 / 13 = 5). If the electrical motor speed is 3,450 rpm, the gearbox reduces this speed by five occasions to 690 rpm. If the electric motor torque can be 10 lb-in, the gearbox increases this torque by a factor of five to 50 lb-in (before subtracting out gearbox performance losses).
Parallel shaft gearboxes often contain multiple gear units thereby increasing the apparatus reduction. The total gear decrease (ratio) depends upon multiplying each individual equipment ratio from each equipment established stage. If a gearbox consists of 3:1, 4:1 and 5:1 gear pieces, the full total ratio is 60:1 (3 x 4 x 5 = 60). In our example above, the 3,450 rpm electric electric motor would have its swiftness reduced to 57.5 rpm by utilizing a 60:1 gearbox. The 10 lb-in electric electric motor torque would be risen to 600 lb-in (before efficiency losses).
If a pinion equipment and its mating gear have the same number of teeth, no decrease occurs and the apparatus ratio is 1:1. The gear is named an idler and its own primary function is to change the path of rotation instead of reduce the speed or boost the torque.
Calculating the gear ratio in a planetary gear reducer is much less intuitive as it is dependent upon the number of teeth of sunlight and band gears. The planet gears become idlers , nor affect the apparatus ratio. The planetary gear ratio equals the sum of the number of teeth on the sun and ring gear divided by the number of teeth on the sun gear. For example, a planetary arranged with a 12-tooth sun gear and 72-tooth ring gear includes a equipment ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear units can achieve ratios from about 3:1 to about 11:1. If more equipment reduction is needed, additional planetary stages may be used.
The gear reduction in a right-angle worm drive would depend 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 begins and the mating worm wheel provides 50 tooth, the resulting gear ratio is 25:1 (50 / 2 = 25).
When a rotary machine such as an engine or electric motor cannot provide the desired output quickness or torque, a equipment reducer may provide a great choice. Parallel shaft, planetary, right-position worm drives are common gearbox types for attaining gear reduction.