A belt drive that uses a timing belt is one of the oldest mechanical inventions. However, despite the fact that such a transmission method was invented a long time ago, it is actively used at present.
Belt section
It is worth mentioning that there are many different belts that can be used in a belt drive. Depending on their section, belts are divided into:
- flat;
- wedge;
- polycline;
- round;
- toothed.
You can also add that there are many directories and other sources that detail V-belts or flat belts. But with toothed belts, everything is a little worse, since it was this type of device that came into use not so long ago. Although in the days of the USSR, OST 38 - 05114 - 76 and OST 38 - 05227 - 81 were developed. These documents clearly stated what the dimensions of the named part should be, as well as how it is necessary to carry out calculations for toothed belts and toothed belts.
Belt Benefits
It is this type of belt that gained its wide distribution due to the fact that it had certain positive characteristics. These benefits include the following:
- The loading capacity of such belts is high.
- The product has small dimensions.
- Sliding of such belts is completely absent due to their design.
- These belts allow you to realize high gear ratios.
- Speed characteristics of gear belts are also very high - up to 50 m / s.
- Due to the small initial belt tension, the impact on the shaft and axle is small.
- Quite a small amount of noise emitted.
- A very high coefficient of performance - up to 98%.
It is also important to understand that the production of belts is carried out with certain requirements, which it must meet. These requirements include:
- oil resistance;
- belt operating temperature range (it should be in the range from -20 to +100 ° );
- resistance to ozone;
- lack of sensitivity to weather conditions.
Belt shape
Currently, timing belts can be divided into several groups depending on the shape of the teeth that it has. There are teeth with a semicircular shape or with a trapezoidal shape.
The advantage of the semicircular shape of the teeth is that they provide a more uniform distribution of tension in the belt, increase the limit of possible loads that it can carry by 40%, as well as a smoother engagement of the teeth. If we talk about such belts in general, then the cost of ordinary and with semicircular teeth is the same, but the performance characteristics of the second type are clearly higher.
These devices consist of several elements:
- Directly the teeth, as well as the top layer of the belt.
- Composite support cord.
- The bottom layer of the belt, consisting of polyamide fabric.
Belt device
Currently, in the engineering industry, drive gear belts are quite widespread. This product is considered very durable, but it has the necessary elasticity.
These products consist of three layers. The first layer is the bearing, and also determines the maximum load that the belt can withstand, and its strength. The production of this layer is carried out from a cord, which is made of either fiberglass or Kevlar.
The second layer of timing gear belts is made of polyurethane or rubber. It should provide the necessary flexibility and elasticity of the entire belt. The last, third layer, is made of nylon or any other durable synthetic material. In order to combine all three layers into one and create a drive belt, the vulcanization process is used.
Benefits of Drive Products
The first and most important advantage of this type of belts is their highest rate of performance, that is, efficiency. Most often, drive belts, regardless of whether they are made of polyurethane or rubber, are used to achieve higher speeds.
Such products fit very well on the pulley, taking the necessary shape, which ensures all the necessary indicators. Another parameter worth highlighting is the very high flexibility of the belt. In order to reduce the risk of a belt fracture in those places where the highest voltage is present, it is equipped with special shaped teeth.
Another fact that you should pay attention to is the distance between the shafts when using belt gears. During the use of drive belts, a small distance between the centers of the shafts is allowed, which ensures an increase in the speed of its elements, and also contributes to an increase in the power that the belt can transmit. It is also worth noting that their use greatly reduces the vibration of the elements even in the case when discontinuous loads are carried out, and slippage is not observed in the system itself.
PU belts
The use of polyurethane timing belts opens up wider possibilities for their use. Due to the wide variety of designs and the large number of options for using such devices, they can be used in a wide variety of industries.
Due to their properties, polyurethane timing belts have found their application among linear and transport equipment. In addition, they can be used in various lifting mechanisms or even in washing installations. The use of toothed belts of this type is possible when installing gates or doors that open automatically, they can be used even in robotics. It can be added that polyurethane belts can be either single-sided or double-sided. In addition, they may have a non-standard coating or an unusual tooth shape.
Timing belt profiles differ in tooth shape. The following types are distinguished:
- trapezoidal profile;
- semicircular profile;
- gear two-sided.
Timing Belt Repair
Consider the process of replacing the toothed belt using the example of a five-cylinder engine. It is worth starting with the fact that to perform this operation on this type of engine, you must have a special tool from VAG
In order to remove the desired part, it is necessary to loosen the vibration damper. It is mounted in front on the crankshaft. After removing the belt, you need to retighten them using a special nozzle, which is designed for a torque wrench. If the engine is four-cylinder, then the replacement process is as follows:
- The piston is installed in the first cylinder in V.M.T.
- The belt cover is removed.
- The belt loosens and is removed.
- A new belt is installed.
It is worth noting that if the cylinder head was removed when replacing the belt, the phases of gas distribution will have to be regulated.