On the surface, it could appear that gears are being “reduced” in quantity or size, which is partially true. When a rotary machine such as for example an engine or electrical motor needs the output speed reduced and/or torque improved, gears are commonly utilized to accomplish the required result. Gear “reduction” specifically refers to the speed of the rotary machine; the rotational rate of the rotary machine is definitely “decreased” by dividing it by a equipment ratio higher than 1:1. A gear ratio higher than 1:1 can be achieved when a smaller equipment (decreased size) with fewer amount of teeth meshes and drives a larger gear with greater quantity of teeth.
Gear reduction gets the opposite effect on torque. The rotary machine’s output torque is increased by multiplying the torque by the gear ratio, less some performance losses.
While in many applications gear reduction reduces speed and raises torque, in additional applications gear decrease is used to improve rate and reduce torque. Generators in wind turbines use gear reduction in this manner to convert a comparatively slow turbine blade acceleration to a high speed capable of generating electricity. These applications use gearboxes that are assembled opposite of those in applications that reduce swiftness and increase torque.
How is gear decrease achieved? Many reducer types are capable of attaining gear decrease including, but not limited by, parallel shaft, planetary and right-position 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 “decrease” or equipment ratio is definitely calculated by dividing the number of teeth on the large equipment by the number of teeth on the small gear. For example, if an electric motor drives a 13-tooth pinion gear that meshes with a 65-tooth gear, 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 swiftness by five occasions to 690 rpm. If the engine torque is usually 10 lb-in, the gearbox boosts this torque by a factor of five to 50 lb-in (before subtracting out gearbox effectiveness losses).
Parallel shaft gearboxes many times contain multiple gear units thereby increasing the gear reduction. The full total gear reduction (ratio) depends upon multiplying each individual gear ratio from each equipment arranged stage. If a gearbox consists of 3:1, 4:1 and 5:1 gear pieces, the total ratio is 60:1 (3 x 4 x 5 = 60). In our example above, the 3,450 rpm electric engine would have its acceleration 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 performance losses).
If a pinion gear and its mating gear have the same amount of teeth, no decrease occurs and the apparatus ratio is 1:1. The gear is called an idler and its main function is to change the direction of rotation rather than decrease the speed or raise the torque.
Calculating the gear ratio in a planetary gear reducer is less intuitive as it is dependent on the number of teeth of sunlight and ring gears. The earth gears become idlers and don’t affect the gear ratio. The planetary equipment ratio equals the sum of the number of teeth on the sun and ring gear divided by the amount of teeth on the sun gear. For example, a planetary set with a 12-tooth sun gear and 72-tooth ring gear has a equipment 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 reduction in a right-angle worm drive is dependent on the amount 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 has 50 tooth, the resulting equipment ratio is 25:1 (50 / 2 = 25).
Whenever a rotary machine such as for example an engine or electric electric motor cannot supply the desired output quickness or torque, a gear reducer may provide a good solution. Parallel shaft, planetary, right-angle worm drives are normal gearbox types for attaining gear reduction.