Micro reduction motors are widely used in communications, smart homes, automobiles, medical, security, robots and other fields. Among them, small module gear transmission has received more and more attention and attention in micro reduction motors, and among them, reduction gears The grease used in the box also plays a boosting role. The main functions of grease are: ① reduce friction and wear and prevent gluing; ② reduce noise; ③ absorb shock and vibration; ④ rust and corrosion resistance; ⑤ heat dissipation, cooling, Eliminate foreign matter; ⑥ Improve gear meshing life, etc.

The gear material used in the reduction gearbox has a great relationship with the selection of grease. Under normal operation of the gear transmission device, the characteristics of the grease must be considered: ① Have appropriate viscosity; ② High load-bearing capacity; ③ Good Wear resistance; ④ Oxidation stability and thermal oxidation stability; ⑤ Anti-emulsification, anti-foaming, rust prevention and corrosion resistance; ⑥ Good fluidity, low freezing point and safe use; ⑦ EP under mixed friction conditions Extreme pressure agents provide properties such as wear protection.

The gear materials in the reduction gearbox usually include metal, powder metallurgy, plastic, MIM, etc. Because of the different materials, the requirements for torque, current, temperature, speed, and noise during output are often also different. At the same time, the requirements of the reduction gearbox The structure will also have different requirements for the properties of the grease, so greases with different properties emerge as the times require.

Generally speaking, ① the more compact the structure of the reduction gearbox, the smaller the volume, the smaller the heat dissipation area, the higher the extreme pressure performance and the better the thermal stability of the grease required; ② Multiple gears meshing During the operation of the transmission, the grease is required to have anti-foaming properties and high adhesion; ③ The operating temperature of the meshing gears changes accordingly as the working torque changes, so the grease is required to have good properties at startup and normal operating temperatures. Excellent viscosity-temperature characteristics and low evaporation; ④ The materials used in the reduction gearbox, such as bearings, oil seals, and different gear materials, require the grease to have good compatibility and oxidation resistance.

Grease is further explained below.

1. Effects of grease on gear transmission and countermeasures:

As can be seen from the table above, grease has a great impact on gear transmission. Choosing a good grease can not only effectively improve the life of gear transmission, but more obviously, it can also reduce the noise of the gear box, so we are talking about gear transmission. What kind of grease is used in the box is particularly important for gear boxes.

2. Grease viscosity selection:

    The output state of the reduction gearbox is closely related to the gear material used and the viscosity of the grease. Generally, for gearboxes with relatively large output torque, in order to extend the service life or ensure that the above failure modes are prolonged or not occur, the gear material is generally made of metal with a higher viscosity. Larger grease has greater adhesion, has better protection and anti-vibration effects on metal materials, and can effectively reduce the noise of the gearbox. Therefore, grease with higher viscosity is generally selected; and for small output torque The reduction gearbox is usually made of plastic. If a grease with a higher viscosity is used, the output current or torque of the gearbox will increase significantly in order to overcome the resistance brought by the viscosity, which will restrict the operation of the gearbox. Therefore, gearboxes with smaller output torque or made of plastic materials usually use less viscous grease.

For high-speed gearboxes, due to the high gear speed, the requirements are generally small starting current or torque, so grease with lower viscosity is generally used.

Generally, greases with different viscosities are not selected based on the structural form, but as a special form of planetary gearbox, the selection of low-speed grease is given below for reference only.

Low speed gear meshing linear speed:

Note:

          d: Low speed stage sun gear pitch circle diameter;

          n: Low-speed sun gear pitch circle speed;

          i: low-speed gear ratio.

3. Selection of grease amount:

The amount of grease in the reduction gearbox determines the gear meshing operation life, noise, etc. Too much grease will increase the cost. The amount of grease used in reduction gearboxes with different structures is different. The amount of grease used in planetary reduction gearboxes is usually based on the gear. 50~60% of the blank volume left by meshing is appropriate; parallel shaft or staggered shaft reduction gearboxes usually have more blank space. The amount of grease is selected based on multiple pairs of meshing gears and relatively low noise; worm gears, surfaces The gear box should be 60% of the tooth space volume of the gear.

4. Color choice:

There is no certain correlation between the color and viscosity of grease, but grease with higher viscosity usually has a darker color, such as red.

The greases used in reduction gearboxes generally include: ① precision grease; ② food-grade waterproof and silencing grease; ③ gear grease; ④ molybdenum disulfide silencing grease, etc.

The color of molybdenum disulfide silencer grease is black. Other greases are generally white, yellow, red, etc. Under normal circumstances, we can choose these colored greases at will.