Speed reducers: main applications and how to improve their operation
Saturday - 18/11/2017 10:33
We could consider speed reducers as a major invention which, without a doubt, see a greater notoriety and presence in current times, being used in practically every machine around us.
But what are the main applications of speed reducers? What elements are they composed of?
What are the main applications of speed reducers?
Speed reducers are used to operate all types of industrial and household machines which need to reduce the speed of an electric motor safely and efficiently. Speed reducers adjust a motor’s speed in order to provide the torque needed by a machine to work properly.
As a transmission system, speed reducer gearboxes stand out due to their high complexity, with a myriad of speed reducer system designs available depending on the needs and specifications of each application.
Elements that compose a speed reducer
Knowing about certain concepts will help us better understand the elements that compose a speed reducer.
The concept of torque
It is a rotational force expressed in units of kilogram per metre, Newton per metre or pound per feet. When torque is combined with an execution time, it turns into a “power”.
An electric motor has a specific force specified in HP, and has an operational speed for the output shaft.
Both characteristics, power and speed, define the torque the motor can provide. The torque will determine whether a load will turn or not.
The combination of power, torque and speed of a motor or gear motor is defined as per the following formula:
W= M (Nm) x w (rad/s).
W =16,4 Nm (maximum torque output in Nm) x speed (at maximum output in rad/s).
10 r.p.m = 10× 1 revoluciónmin×1 min60 s×2π rad1 revolución= 10 x 2 x π60= 1,047 rad/s
W =16,4 Nm x 1,047 rad/s= 17 W.
1cv= 735,39875W = 0.98632HP
It is a transmission mechanism. It is composed of a set of mechanical components that enable the proper speed reduction and increase in torque transmission. All of its items are just as important, and they need a perfect geometry and composition for the proper operation of the system. We are referring to gears, plain bearings, crown wheels, washers, pulleys, pinions…
Overall, before starting an electromechanical engineering project that requires an actuation, we should answer questions that are vital to obtain an optimal final outcome. Being aware of the types of speed reducers and their advantages is important. The selection will depend on the type of motion we seek, the power we require, or the space we have in the machine. Here we show you the main types of speed reducers you can find.
Types of speed reducers
Planetary speed reducer
Due to its great precision and reliability, many automatic transmissions nowadays use this type of speed reducer.
Which elements compose a planetary speed reducer?
Sun: The central gear. It is larger and rotates around the central shaft.
Carrier: Its purpose is to hold up to 3 satellite gears of the same size which engage with the central gear, a.k.a. sun.
Ring gear: An external ring (with teeth on its inner side) engages with the satellites and encloses the entire epicyclic gear train. Additionally, the central shaft may also become the rotational centre for the outer ring, which makes it easy to change directions.
Planetary gear motors
It is the most common type of gear, and its main feature is that its teeth are set up on parallel axes. This type of spur gear is used when motion has to be transferred from one shaft to another one that is close and parallel.
These are its features
Used for transferring a great amount of power (around 500 KW)
Provides a constant and stable speed ratio.
It is more efficient when compared to a helical gear with the same size.
They run smoother and more silently when compared to spur gears; this is because of the oblique manner in which their teeth interact in relation to the rotation axis.
They can be set up parallel to each other or, generally, at 90 degrees. If this is the case, and helical gears are crossed, they are combined with a worm gear.
What are its features?
It lasts longer; and is ideal for high load applications.
Its angled teeth operate gradually, allowing the operation of the gear to be smoother and more silent.
Load is distributed across several shafts, resulting in less wear.
Gear motors guide
Classification of gear motors based on the disposition of their shafts
Parallel shaft gear motors
This is a type of gear motor that uses gears to accomplish an optimal speed reduction. The shaft of the motor and the gear motor are in parallel axes; this disposition allows for very flat gearboxes.
The parallel shaft gear motor can use three types of gears to accomplish the transmission; choosing one or the other will depend on the final application.
What are the advantages of a parallel shaft gear motor?
A compact design, which translates into a lower weight and smaller space
They reach powers of up to 200 KW.
Low vibration, low noise levels.
Worm / 90-degree gear motor
This can be considered as the simplest gear motor; it is composed of a toothed worm wheel, normally made of bronze with a steel shaft in its centre.
This wheel is constantly in contact with a steel screw shaped as a worm (hence its name). One of its main features is that its shafts are set up in a 90-degree angle.
How can the operation of gear motors be improved?
There are four basic parameters which allow for a better quality product or solution based on their analysis.
The analysis and correction of mechanical noise levels
Gear motors should be subjected to tests using frequency measurement equipment before their release on the market. It is very important to take note of mechanical vibrations and for your gear motor supplier to know how to use vibration measurement instruments to prevent uncomfortable frequencies.
Optimal torque measurement
The optimal measurement of the starting torque, output torque and rated torque guarantees the proper transmission of the motion and the adaptability of the machine or application.
Energy efficiency of the speed reducer is another item to keep in mind when choosing one model or the other. The disposition of the gear train, the disposition and characteristics of rolling bearings or the surface treatments of components enhance performance across the entire system.
Service life tests
Tests are carried out in laboratories to measure the resistance, limits and the speed reducer service life. Gear motor suppliers that have these laboratories and the testing technologies they offer can guarantee buyers the delivery of quality gear motors.