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 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 velocity of the rotary machine; the rotational velocity of the rotary machine is “reduced” by dividing it by a equipment ratio higher than 1:1. A gear ratio higher than 1:1 is definitely achieved when a smaller equipment (reduced size) with fewer number of teeth 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 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 additional applications gear reduction is used to increase speed and reduce torque. Generators in wind generators use gear reduction in this fashion to convert a comparatively slow turbine blade velocity to a higher speed capable of generating electricity. These applications make use of gearboxes that are assembled opposite of these in applications that reduce velocity and increase torque.
How is gear reduction 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 equipment with a specific number of the teeth meshes and drives a larger gear with a greater number of teeth. The “reduction” or equipment ratio can be calculated by dividing the amount of teeth on the large gear by the amount of teeth on the tiny gear. For example, if a power motor drives a 13-tooth pinion gear that meshes with a 65-tooth equipment, a reduced amount of 5:1 is usually achieved (65 / 13 = 5). If the electrical motor speed is definitely 3,450 rpm, the gearbox reduces this rate by five instances to 690 rpm. If the motor torque is 10 lb-in, the gearbox raises this torque by one factor of five to 50 lb-in (before subtracting out gearbox efficiency losses).
Parallel shaft gearboxes many times contain multiple gear units thereby increasing the apparatus reduction. The full total gear reduction (ratio) depends upon multiplying each individual gear ratio from each gear established stage. If a gearbox consists of 3:1, 4:1 and 5:1 gear units, the full total ratio is 60:1 (3 x 4 x 5 = 60). In our example above, the 3,450 rpm electric engine would have its swiftness decreased 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 efficiency losses).
If a pinion equipment and its mating gear have the same amount of teeth, no decrease occurs and the gear ratio is 1:1. The apparatus is called an idler and its principal function is to change the path of rotation rather than reduce the speed or raise the torque.
Calculating the gear ratio in a planetary equipment reducer is less intuitive since it is dependent upon the number of teeth of the sun and band gears. The planet gears become idlers and do not affect the gear ratio. The planetary gear ratio equals the sum of the amount of teeth on sunlight and ring equipment 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 includes a equipment ratio of 7:1 ([12 + 72]/12 = 7). Planetary gear pieces 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 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 begins and the mating worm wheel provides 50 the teeth, the resulting equipment ratio is 25:1 (50 / 2 = 25).
When a rotary machine such as an engine or electric engine cannot provide the desired output swiftness or torque, a equipment reducer may provide a good solution. Parallel shaft, planetary, right-position worm drives are normal gearbox types for achieving gear reduction.