Micro geared motors are widely used in communication, smart home, automobile, medical, security, robotics and other fields. Among them, small modulus gear drives have received more and more attention and attention in micro and small geared motors. Among them, reduction gears The grease used in the box also plays a boosting role. The main functions of the grease are: ①Reduce friction and wear and prevent gluing; ②Reduce noise; ③Absorb shock and vibration; ④Antirust and corrosion resistance; Eliminate foreign matter; ⑥ Improve gear meshing life, etc.

The gear material used in the reduction gearbox has a lot to do with the selection of the grease. Under the normal operation of the gear transmission, the characteristics of the grease should be considered: ① with suitable viscosity; ② high bearing capacity; ③ good Wear resistance; ④ oxidation stability and thermal oxidation stability; ⑤ anti-emulsification, anti-foaming, rust 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 different materials, the requirements for torque, current, temperature, speed, and noise during output are often different. The structure will also have different requirements for the characteristics of the grease, so greases with different characteristics emerge as the times require.

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

The following is a description of the grease.

1.Influence of grease on gear transmission and countermeasures:

    Note:“√”an influence

It can be seen from the above table that grease has a great influence on gear transmission. Choosing a good grease can not only effectively improve the life of gear transmission, but also reduce the noise of the gear box. What kind of grease is used in the box is particularly important for the gearbox.

2.Choice of grease viscosity:

The output state of the reduction gear box, the gear material used and the viscosity of the grease are closely related. Usually, the gear box with a relatively large output torque, in order to achieve the life or ensure that the above failure modes are prolonged or not occurred, the gear material is generally made of metal, and the viscosity is relatively high. Larger greases have larger adhesion, better protection and anti-vibration effects on metal materials, and can effectively reduce the noise of the gearbox. Therefore, greases with higher viscosity are generally used; while for smaller output torques Usually the gear material is plastic. If the grease with higher viscosity is used, the output current or torque of the gearbox will increase significantly in order to overcome the resistance caused by the viscosity, which will restrict the operation of the gearbox. Therefore, gear boxes with small output torque or plastic materials are usually selected with less viscous grease.

For high-speed gearboxes, due to the high speed of the gears, the requirement is generally that the starting current or torque is small, so the grease with lower viscosity is generally selected.

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

Low-speed gear meshing line speed:

note:

          d: Low-speed sun gear pitch diameter;

          n: Low-speed sun gear pitch circle speed;

          i: Low-speed gear ratios.

3. Choice of oil amount

The amount of grease in the reduction gearbox determines the gear meshing operating life, noise, etc. Too much will increase the cost. The amount of grease used in the reduction gearbox of different structures is different. The planetary reduction gearbox usually chooses the amount of grease based on gears 50~60% of the blank volume left by meshing is appropriate; while the parallel shaft or staggered shaft reduction gearbox usually has more blank space, the selection of grease quantity is based on the relative low noise of multiple pairs of meshing gears; worm gear, surface The gearbox is preferably 60% of the volume of the tooth slot of the gear.

4. Choice of colors:

There is no certain correlation between the color and viscosity of the grease itself, but usually the grease with higher viscosity will have a stronger color, such as red.

The grease used in the reduction gearbox generally includes: ① precision grease; ② food grade waterproof and sound-absorbing grease; ③ gear grease; ④ molybdenum disulfide sound-absorbing grease, etc.

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