In life, there are many belt drives and chain drives. Bicycles are chain drives, while toy industry also uses belt drives to make use of its low noise and overload protection. Generally, open transmission is used for toy belt transmission. The advantages of belt transmission are: (1) the distance to transmit motion is far; (2) Stable operation and low noise; (3) Self starting overload protection by slipping; (4) The structure is relatively simple, the design accuracy is not high, and it can also meet the requirements of many toy actions.

Disadvantages of belt drive: (1) Large size, many toy products do not have enough space to use; (2) The efficiency of transmission speed reduction is relatively low, and the theoretical speed reduction is the ratio of big wheel radius to small wheel radius, which is the speed reduction ratio; (3) The service life of the belt is not long, which will lead to a short service life of the product (although the life of the toy is not required to be long); (4) Inaccurate transmission (belt slip).

Belts: The most widely used belts in toys are round belts and square belts, usually made of rubber. Belts are generally molded by injection molding. For some small toy factories, they don't make belts (rubber bands) by themselves. Instead, they buy them cheaply. Generally, a rubber band costs a few cents, while opening an additional set of molds costs tens of thousands of yuan.

The belt pulley is generally made of copper pulley and POM plastic pulley. Generally, the small driving wheel (the belt pulley directly hit on the motor shaft) will use a metal copper wheel, while the large wheel will use a plastic POM wheel. In terms of mechanical principle, the belt should rub against the groove side of the pulley, which is the most effective. The pulley on the toy is also designed in this way, but sometimes the actual situation is that the belt is directly pressed on the pulley.

The pulley shall have independent space in the teeth. Because the belt is rubber and the pulley is mostly plastic POM pulley, but for other transmission structures such as gears and motors, the noise is very high due to errors in actual operation, so noise reducing gear oil will be used. This oil will make the rubber belt slip with the pulley, and will be absorbed by the rubber, thus reducing the service life of the belt. Therefore, the entire belt and pulley should be placed in an independent space when designing teeth, To prevent oil splashing onto the belt.

Common problems and solutions

Insufficient life of the belt: that is, the toy cannot pass the life test, which is mainly determined by the characteristics of the belt, but the life can be extended by solving unnecessary losses. For example, ensure that the driving pulley and driven pulley are in the same plane in the direction of belt force, and maintain the appropriate axle distance between belts.

Insufficient power of belt drive: belt slipping. It is necessary to check whether there is lubricating oil splashing on the belt pulley or belt. It is also possible that the belt pulley has been injected with a lot of mold release agent during the injection molding process. It is also possible that the axle distance between two belt pulleys is large, which makes the force insufficient. If necessary, a transition pulley can be added to increase the contact area between the belt and the belt pulley.

An overload protection device is added to make the working force limit of the protection device less than the pulley slipping force, so as to reduce the pulley slipping and extend the pulley life.