There are so many kinds of gear motors on the market. It will be hard for those who are new to gear motor industry to recognize each type of it. It can be a long process of learning and stimulating knowledge of it. This passage would demonstrate most keys points of a planetary gear motor, which is the most common type in gear motors.
Before talking about how a planetary gear motor works, we should have some basic knowledge of it first. As introduced in the former passage, a gear motor is generally made up of a set of gears, called gearboxes/gearheads, and a motor, which is used to change speed and torque. That’s to say, a planetary gear motor indicates a motor with a planetary gearbox/planetary gearheads. If combined with a DC motor, it’s called dc planetary gear motor, of which planetary gear motor 12VDC and 24 volt DC planetary geared motor are the general types. Therefore, we must learn the structure of a planetary gearbox.
Planetary gearheads normally consist of three parts: a sun gear, planet gears (or called “satellite gears”), and a ring gear. The sun gear is generally placed in the center, while planet gears orbit around the sun gear and receive torque from it. As for the ring gear, the outer ring gear (refers to the housing below) meshes with planet gears. Here is a picture of micro planetary gear motor.
How Does A Planetary Gear Motor Work?
When the sun gear rotates under the drive of the motor, the planet gears begin to rotate since they mesh with the sun gear. At the same time, the planet gears mesh with the ring gear on the inner wall of the planetary gearheads housing. Eventually, under the rotation driving force, the planetary gear will rotate in the same direction as the sun gear, forming a “revolution” movement around the sun gear.
Usually, each planetary gearbox will have multiple planetary gears (also known as “multiple stages”), which will rotate around the central sun gear under the combination of the input shaft and the sun gear’s rotational driving force, and transmit the output torque of the planetary gearbox.
It is easy to see that the input speed of the motor of the planetary gearbox (namely, the speed of the sun gear) is higher than the output speed, which is why it is usually called planetary gear reduction motor. The speed ratio between the motor and the output speed is called the reduction ratio of the planetary reducer, or “gear ratio” for short. It is usually indicated by the letter “i” in the product specifications. It is determined by the number of teeth of the ring gear and the sun gear. In general, the gear ratio of the planetary reducer with a single-stage reduction gear is usually between 3 and 10. A planetary gear motor with a gear ratio of more than 10 needs to use a two-stage (or more) planetary gearheads.
The Advantages of the Planetary Gear Motor
- High torque: With more teeth in contact, the mechanism is able to transmit and withstand more torque in a more uniform manner.
- Durable & Efficient. The bearing can reduce the friction by connecting the shaft directly to the gearbox. It allows for better rolling and smooth operation. The efficiency is improved as well.
- Easy to install. Its mechanism is contained in a cylindrical gearbox, which can be installed in almost any space.
- Impressive precision: The angle of rotating is fixed, thus improving the accuracy and stability of the rotary motion.
- Compact size. Due to the planetary structure that multiple gears are meshed together and orbit around a sun gear, the planetary gear motor can be compact and small. 3.4mm, 4mm planetary gear motor and 6mm planetary gear motor are achieved.
- Low noise. The multiple gears enable more surface contact. Rolling is much softer and jumps are virtually nonexistent.
Planetary gear motors are often used when you need to reduce speed and increase torque heavily in a limited space. As for the specific applications, you can refer to these cases. However, the parameters need to be customized in actual use cases, like diameter, voltage, input speed, torque, etc. If you need customization of gear motor, ZHAOWEI can be a good choice, who is experienced in providing various planetary drive systems.