2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16
Modern industry, engineering and other industries use a variety of mechanisms in their work. They ensure the operation of units, vehicles, motors, etc. One of the popular, frequently used devices is the V-belt drive.
The presented mechanism includes several categories of structures. They differ in geometric parameters, purpose, approach to the implementation of the tasks assigned to the mechanism. What are the presented devices will be discussed further.
General characteristics
The V-belt transmission device involves the use of a special method of actuating the entire mechanism. In this case, the energy produced in the torque process is used. This is provided by a belt drive. It uses mechanical energy, which it then transfers to another mechanism.
This design consists of a belt and a minimum of two pulleys. The first of these structural elements is most often made of rubber. V-belt drive belt is made ofmaterial that has undergone special processing. This allows the presented element to be resistant to medium and small mechanical stress, elevated temperatures.
Among belt drives, V-belt is the most popular. This design is often used today in the manufacture of cars, as well as other types of vehicles.
Design Features
The design of the presented variety of mechanical power transmission includes V-belt pulleys and a belt. The last of these elements has a wedge-shaped shape. The pulleys are made in the form of metal discs. They have branches evenly distributed around the circumference. They hold the belt in position on the surface of the pulleys.
The tape can be of two types. It can have teeth or have a completely smooth surface. The choice depends on the purpose of the mechanism. Previously, the presented design was used in many systems of various categories of vehicles.
Today, the presented type of mechanical energy transmission is used in water pumps and machine generators. In heavy automotive equipment, a similar system is installed in order to drive the power steering. This system has a hydraulic pump. It is in it that a similar design is used. V-belt drives are also installed in air-type compressors. They are designed for vehicle brake boosters.
Requirements for elementsdesigns
V-belts have a relatively small thickness. This allows to significantly reduce the dimensions occupied by the system. However, this fact requires a special approach to the organization of the pulley geometry. To prevent the tape from jumping off, the outer surface of the disks has special grooves. They hold the belt in place.
The size of the pulley itself is selected in accordance with the gear ratio. If it is necessary to create a reduction gear, the driven pulley will be larger than the leading structural element. There is also an inverse relationship.
In the manufacture of the belt tape, special soft materials are used that should not lose their performance in all weather conditions. In frost and heat, the belt remains flexible. It is for this reason that it is not allowed to install another material instead of a special tape. This will damage the unit.
Varieties
V-belt transmission can be made in several configurations. There are several popular types of presented mechanisms. One of the simplest is an open system. The pulleys rotate in the same direction, the axes move in parallel.
If the discs move in opposite directions while maintaining the parallelism of the strips, a cross-type of the system appears. If the axes cross, it will be a semi-cross variety.
If the axes intersect, there is an angular transmission. She appliesstepped pulleys. This design allows you to influence the speed at the angle of the driven shaft. The speed of the drive pulley remains constant.
The idle pulley gear allows the driven pulley to stop moving while the drive shaft continues to rotate. Idler pulley gearing promotes self-tensioning of the belt.
Belt
V-belts belong to the category of traction structural elements. It must ensure the return of the required energy without slipping. The tape must have increased strength, wear resistance. The blade should adhere well to the outer surface of the discs.
Width of straps can vary considerably. In the manufacture of rubberized cotton, woolen materials, leather. The choice depends on the operating conditions of the equipment.
The tape can be made of cord fabric or cord cord. These are the most reliable, flexible and fast varieties.
Modern engineering today often uses toothed belts. They are also called polyamide. There are 4 protrusions on their surface. They mesh with the corresponding elements on the pulleys. They perform well in high speed gears, applications with small pulley spacing.
Estimated pulley diameter
The calculation of V-belt transmission begins with determining the diameter of the pulley. To do this, you need to take two cylindrical rollers. Their diameter is D. This value is set for each size of the groove section. In this case, the contact of the rollerspasses at the level of the diameter.
Two rollers of the type shown must be placed in the groove. The surfaces must touch. Between the tangent planes that form the rollers, it is necessary to measure the distance. They should run parallel to the pulley.
A special formula is used to calculate the disc diameter. She looks like this:
D=RK - 2X, where RK is the distance measured between the rollers, mm; X is the distance from the diameter of the disc to the tangent that fits the roller (runs parallel to the axis of the disc).
Transfer calculation
V-belt transmission is calculated according to the established methodology. In this case, the indicator of the transmitted power of the mechanism is determined. It is calculated using the following formula:
M=Mnom. K, where Mnom. – rated power consumed by the drive during operation, kW; K is the dynamic load factor.
When making calculations, an indicator is taken into account, the probability of distribution of which in the stationary mode is no more than 80%. The load factor and mode are presented in special tables. In this way, the speed for the belt can be determined. It will be:
SR=πD1ChV1/6000=πD2ChV2/6000, where D1, D2 are the diameters of the smaller and larger pulleys (respectively); CV1, CV2 - the rotational speed of the smaller and larger disk. The diameter of the smaller pulley must not exceed the rated speed limit of the belt. She is 30m/s.
Calculation example
To understand the calculation methodology, it is necessary to consider the technology of this process on a specific example. Suppose it is necessary to determine the gear ratio of the V-belt drive. At the same time, it is known that the power of the drive disk is 4 kW, and its speed (angular) is 97 rad/s. At the same time, the driven pulley has this indicator at the level of 47.5 rad / s. The diameter of the smaller pulley is 20mm and the larger pulley is 25mm.
To determine the gear ratio, it is necessary to take into account belts with a normal section, made of cord fabric (size A). The calculation looks like this:
IF=97/47, 5=2, 04
Determining the diameter of the pulleys from the table, it was found that the smaller shaft has a recommended size of 125 mm. The larger shaft when the belt slips 0.02 will be:
D2=2.041.25(1-0.02)=250mm
The result fully complies with the requirements of GOST.
Example of calculating the length of belts
The V-belt length can also be determined using the presented calculation. First you need to calculate the distance between the axes of the disks. To do this, apply the formula:
R=SD2
С=1, 2
From here you can find the distance between the shafts:
P=1, 2250=300mm
Next, you can determine the length of the belt:
D=(2300 + (250-125)²+1.57(250+125))/4300=120.5cm
The inner length of the belt in size A according to GOST is 118 cm. In this case, the estimated length of the tape should be 121.3 cm.
Calculation of system operation
Determining the dimensions of the V-belt transmission, it is necessary to calculate the main indicators of its operation. First you need to set the speed at which the tape will rotate. For this, a certain calculation is applied. The data for it was given above.
S=970.125 / 2=6.06 m/s
In this case, the pulleys will rotate at different speeds. The smaller shaft will turn around with this indicator:
CBm=3097 / 3, 14=916 min -¹
Based on the calculations presented in the relevant reference books, the maximum power that can be transmitted using the presented belt is determined. This figure is equal to 1.5 kW.
To test the material for durability, you need to make a simple calculation:
E=6, 06/1, 213=5.
The resulting indicator is acceptable by GOST, according to which the presented belt is made. Its operation will be quite long.
Design flaws
V-belt drive is used in many mechanisms and units. This design has many advantages. However, it also has a whole list of shortcomings. They are large in size. Therefore, the presented system is not suitable for all units.
At the same time, the belt drive is marked with a low bearing capacity. This affects the performance of the entire system. When using even the most modern materials, the life of the belt leaves much to be desired. It is erased, torn.
The gear ratio is a variable value. This is due to the slip of the flat shaped belt. When using the presented design, the shafts are subjected to a high mechanical impact. Also, the load acts on their supports. This is due to the need to pre-tension the belt. In this case, additional elements in the design are used. They dampen line vibrations by keeping the strip on the surface of the pulleys.
Positives
V-belt transmission has a lot of advantages, so today it is used in various units quite often. This design ensures high smoothness of operation. The system operates almost silently.
In case of inaccuracies in the installation of pulleys, this deviation is compensated. This is especially noticeable in the angle of crossing, which is determined between the disks. The load is compensated in the process of belt slippage. This allows you to somewhat extend the life of the system.
The belt type transmission compensates for the pulsations that occur when the engine is running. Therefore, you can do without installing an elastic coupling. The simpler the design, the better.
It is not required to lubricate the presented mechanism. Savings are manifested in the absence of the need to purchase consumables. Pulleys and belt can be easily replaced. The cost of the presented items remains acceptable. Mounting the system is simple.
When using this system, it turns out to create an adjustable gear ratio. The mechanism has the ability to work at high speeds. Even if the tape breaksother elements of the system remain intact. In this case, the shafts can be at a considerable distance from each other.
Having considered what a V-belt drive is, we can note its high performance. Thanks to this, the presented system is used today in many units.
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