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 for example an engine or electric motor needs the output speed reduced and/or torque improved, gears are commonly utilized to accomplish the desired result. Gear “reduction” particularly refers to the swiftness of the rotary machine; the rotational swiftness of the rotary machine is “reduced” by dividing it by a gear ratio greater than 1:1. A gear ratio greater than 1:1 is definitely achieved when a smaller equipment (decreased size) with fewer amount of tooth meshes and drives a larger gear with greater quantity of teeth.
Gear reduction has the opposite influence on torque. The rotary machine’s output torque is improved by multiplying the torque by the gear ratio, less some efficiency losses.
While in lots of applications gear decrease reduces speed and boosts torque, in other applications gear reduction is used to increase speed and reduce torque. Generators in wind turbines use gear decrease in this fashion to convert a comparatively slow turbine blade rate to a high speed capable of producing electricity. These applications use gearboxes that are assembled opposite of those in applications that decrease rate and increase torque.
How is gear reduction achieved? Many reducer types can handle attaining gear reduction including, but not limited to, parallel shaft, planetary and right-angle worm gearboxes. In parallel shaft gearboxes (or reducers), a pinion gear with a certain number of teeth meshes and drives a larger gear with a lot more teeth. The “reduction” or gear ratio is certainly calculated by dividing the amount of teeth on the large equipment by the amount of teeth on the small gear. For instance, if an electric motor drives a 13-tooth pinion equipment that meshes with a 65-tooth equipment, a reduction of 5:1 is achieved (65 / 13 = 5). If the electric motor speed is 3,450 rpm, the gearbox reduces this rate by five occasions to 690 rpm. If the electric motor torque is 10 lb-in, the gearbox boosts this torque by one factor of five to 50 lb-in (before subtracting out gearbox performance losses).
Parallel shaft gearboxes often contain multiple gear pieces thereby increasing the gear reduction. The full total gear decrease (ratio) depends upon multiplying each individual gear ratio from each equipment arranged stage. If a gearbox includes 3:1, 4:1 and 5:1 gear sets, the full total ratio is 60:1 (3 x 4 x 5 = 60). Inside our example above, the 3,450 rpm electric electric motor would have its acceleration reduced to 57.5 rpm by using a 60:1 gearbox. The 10 lb-in electric engine torque would be increased to 600 lb-in (before effectiveness losses).
If a pinion gear and its mating gear have the same number of teeth, no decrease occurs and the gear ratio is 1:1. The gear is called an idler and its main function is to change the path of rotation rather than reduce the speed or boost the torque.
Calculating the gear ratio in a planetary gear reducer is much less intuitive as it is dependent on the amount of teeth of sunlight and ring gears. The planet gears act as idlers , nor affect the apparatus ratio. The planetary equipment ratio equals the sum of the amount of teeth on the sun and ring gear divided by the number of teeth on the sun gear. For example, a planetary established with a 12-tooth sun gear and 72-tooth ring gear has a gear ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear units can perform ratios from about 3:1 to about 11:1. If more equipment reduction is needed, additional planetary stages can be used.
The gear decrease in a right-angle worm drive would depend on the amount of threads or “starts” on the worm and the amount of teeth on the mating worm wheel. If the worm has two starts and the mating worm wheel offers 50 the teeth, the resulting equipment ratio is 25:1 (50 / 2 = 25).
Whenever a rotary machine such as an engine or electric motor cannot supply the desired output quickness or torque, a equipment reducer may provide a great choice. Parallel shaft, planetary, right-angle worm drives are common gearbox types for attaining gear reduction.