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# Miniature Gear Motor Knowledge

Jan 04, 2018

Miniature gear motor knowledge

The TTMOTOR DC Micro Gear Motor is a combination of a miniature DC motor and a precision gear unit. Users in the selection of DC motor, often because of the motor speed is too high or the torque is too small to meet the needs, this time, the choice of gear motor is the most appropriate and most direct solution.

The miniature DC gear motor produced by our company adopts the most commonly used miniature DC motor. The gear box has a diameter of 8mm-52mm and a square-shaped gear motor with a large diameter of 100mm. It is applied to 1.5V to 24V voltage and some 120V, 220V High-voltage motors, the lowest speed can be 0.3 per minute to thousands of revolutions, torque in a wide range of 100N.M.

Gear motor calculation

1. Speed n = nm ÷ i (rpm) nm-motor speed, i-gear box total gear ratio.

2. Torque T = Tm × i × ηg ÷ 1000 (kgcm) Tm-motor output torque (gcm), i-gearbox total reduction ratio, ηg-gearbox total efficiency (%).

3. Gearbox total efficiency ηg = η1 × η2 × η3 × η4, η1-first gear efficiency, η2-second gear efficiency, η3-third gear efficiency, each gear efficiency of about 95 %.

4. Input power P1 = U × I (W) U-voltage (V), I-current (A).

5. Output power P2 = T × n ÷ 97.5 (W) T-torque (kgcm), n-speed (rpm).

6.Gear motor total efficiency η = P2 ÷ P1 × 100 = ηm × ηg (%), ηm-motor efficiency.

DC motor structure and characteristics

The use of mass-produced micro-DC motor, with good electrical and mechanical properties and consistency, can maintain the best noise and the best torque motor.

Due to the volume and brush commutator limitations, the DC motor speed is generally in the range of 3000-12000 rpm. As the speed increases, the working life of the motor will be significantly reduced, which is a major disadvantage of DC brush motors; (if Customers require a long life, the need for additional, I Division optional long-life brushless motor.)

At the same time, our precision low-noise motor, equipped with varistor inside, in order to reduce the electromagnetic interference to the working environment, can also be optional circuit devices to reduce sparks when the motor work.

The operating life of a motor depends mainly on the mechanical wear and electrochemical corrosion of the brushes and commutator and can be operated continuously for 300 to 500 hours at rated load torque and speed. The same size brushless motor life can reach 5000-10000 hours.

Gearbox structure and characteristics

The load torque of a DC gear motor (also referred to as a DC geared motor) is directly related to the rotational speed and the current. The rotational speed decreases linearly with the increase of the load and the current increases linearly. Selection of specifications, it should try to work near its maximum efficiency point in order to obtain the ideal running performance, working life and stability characteristics.

In general, DC gearmotors are used in the same environment as miniature DC motors. Special requirements such as ambient temperature, overload conditions, current limits, etc. must be specified beforehand.

The working life of the gearbox generally exceeds the working life of the DC motor, which can usually reach 1000 to 3000 hours. Our minimum life reducer can be more than 1800 hours, the longest to 5000 hours.

The total reduction gear box ratio is generally 1: 4 to 1: 1000 range. Specially designed to achieve a larger reduction ratio, but a large reduction gear box does not allow "turn", that is, the output shaft of the gear box can not be used as a drive shaft, forcibly reversed.

Such as the common market 37GB reducer, our maximum reduction ratio can be done 2430: 1.

For example, 36MM planetary reducer, our maximum reduction ratio can reach 23730: 1.

Due to the limited gear strength, when the total transmission is large, the gear motor may not be able to withstand the stall torque, the load torque can not exceed the maximum allowable short-time load torque. Gear box consists of multi-stage gear pair. Each stage includes a pair of intermeshing gear pairs consisting of plate gears and pinions. The first pinion is mounted on the motor's output shaft. The bearings used in the output shaft of the gearbox are usually oil-lubricated bearings made of sintered copper or iron material.