The V-belt (formerly known as the V-belt) is a transmission belt with an isosceles trapezoid cross-section, and its working surface is two sides.
V-belts are widely used for power transmission on electric and internal combustion engine driven equipment. With the development of science and technology, the V-belt has been constantly changing in terms of material and structural shape, adapting to the needs of high power, high speed, long life, small deformation and small footprint, and its application range is becoming more and more extensive.
Varieties and structures of V-belts
V belts are generally classified according to belt structure, use, belt cross-sectional shape and size.
Classification by belt structure
Cloth-covered V-belt: V-belt with a cloth-covered outer layer.
Cut Side V-belt: A V-belt with a cut side (i.e. no wrap) on the sides.
Classification by belt core structure
Cord core V-belt: V-belt with cord as the strength layer.
Cord Core V-belt: V-belt with rope as the strength layer.
Classification by V-belt usage
Industrial V-belts: V-belts used on industrial and mining machinery.
Automobile V-belt: V-belt (formerly called fan belt) specially used for internal combustion engines such as automobiles and tractors.
Agricultural V-belt: A V-belt dedicated to work machinery such as harvesters.
Structure of the V-belt
Ordinary V-belt
Ordinary V-belt, wedge angle is 40°, relative height (ratio of belt thickness to section width) is about 0.7.
structure
Ordinary V-belts are composed of wrapping layers, stretch adhesive layers (top adhesives), tensile layers and compression adhesive layers (bottom adhesives). The tenacity layer is composed of multiple layers of cords or single-row cords. The ratio of belt top width to belt height is 1.6.
The role of each part
(1) The cladding layer is composed of plain rubber canvas diagonally cut at 45°. It has excellent telescopic and frictional properties. It connects all parts into a whole, protects other parts from wear and corrosion, and can increase the V-belt’s performance. Stiffness.
(2) The tensile rubber layer is composed of rubber with high elasticity and excellent tensile properties, which can withstand the tensile stress of the V-belt during operation and bending, and play a buffering protection role for the cord or cord of the strength layer.
(3) The strength layer is the skeleton of the V-belt, which is composed of rubber cords or dipped cords, and bears the tensile stress generated by the V-belt during operation.
(4) The V-belt of the buffer rubber rope core is around the rope of the strength layer, and there is a layer of rubber with good adhesion strength to the rope, which is the buffer rubber. It acts as a fixed cord and absorbs the dynamic shear stress generated by the deformation of the V-belt at high speeds.
(5) The compression rubber layer is composed of rubber with excellent bending fatigue resistance. It can withstand the compressive stress generated by the V-belt during operation and bending, maintain the rigidity and elasticity of the V-belt, and increase the cross-section of the V-belt and the belt. The friction contact surface of the wheel is used to improve the transmission efficiency.
Narrow V-belt
Narrow V-belt with a wedge angle of 40° and a relative height of about 0.9.
structure
Narrow V-belts are composed of wrapping layers, stretch adhesive layers, tenacity layers and compression adhesive layers. The strength layer is composed of multiple layers of rubber cord or single row of dipped cords.
Structural features
(1) The ratio of the width of the top surface of the belt to the height of the belt is 1.1~1.2. Compared with the ordinary V-belt, the width of the belt is reduced by about one third, so the lateral stiffness of the belt is large.
(2) The top surface of the belt is in the shape of a bow, which can keep the rope cores neatly arranged after being stressed, so the core of the strength layer is evenly stressed, and each rope can fully play its role. Its load bearing capacity can reach 1/3~1/6 of the ultimate bearing capacity of the strength layer rope core.
(3) The discharge position of the tension layer rope is slightly higher than that of the ordinary V-belt, so the neutral layer is moved up, and the height of the compressed rubber layer is correspondingly increased. Due to the upward movement of the force position of the narrow V-belt, the resultant force acting on the pulley groove is closer to the edge of the pulley than the ordinary V-belt. In this way, with the same outer diameter of the pulley, the power transmitted by the narrow V-belt is greater than that of the ordinary V-belt. Due to the increased height of the compression rubber layer, the effective contact surface between the V-belt and the pulley is also increased. Under the condition of the same unit pressure, the narrow V-belt has a greater friction force on the pulley than the ordinary V-belt, so its carrying capacity is correspondingly increased.
(4) The two sides of the belt are concavely curved, so when the V-belt is bent on the pulley, its two sides are always in good contact with the pulley groove, which increases friction.
(5) The wrapping layer is a special rubber canvas, called flexible wrapping or wide-angle wrapping. The angle between the warp and the weft is 120°, and the angle between the warp and the weft and the longitudinal direction of the V-belt is 60°. °. The wrapping cloth of this structure makes the V-belt very flexible, and it is easy to bend even when wrapped on a pulley with a small diameter
(6) Add a layer of oriented fiber film between the strength layer and the compression layer. This layer of film is composed of sizing containing oriented fibers. Its function is to increase the lateral stiffness of the narrow V-belt and prevent the position of the tension layer cord from being displaced.
Due to the above-mentioned structural characteristics, the narrow V-belt has many advantages: at the same speed, the transmission capacity of the narrow V-belt can be increased by 0.5~1,5 times than that of the ordinary V-belt; when transmitting the same power, the structure size of the narrow V-belt Compared with ordinary V-belts, it can be reduced by 50%, the service life is significantly prolonged, the limit speed can reach 40~50/s, and the transmission efficiency can reach 90~97%; in addition, the narrow V-belt can also shorten the transmission center distance, and the pulley Wheel width can be reduced. The narrow V-belt also reduces the centrifugal stress during operation due to the smaller mass per unit length, which is beneficial to prolong its service life.
Wide V-belt
The relative height of the wide V-belt is about 0.3. The top and bottom surfaces of the wide V-belt are toothed or not, and are usually used in the power transmission of belt-type continuously variable transmissions, also known as variable-speed V-belts. Due to the simple structure, easy manufacture, smooth transmission, vibration absorption, wide adaptability, convenient maintenance and low manufacturing cost, the belt-type continuously variable transmission has developed rapidly.
Variety classification
Wide V-belts can be divided into four types according to their top and bottom surfaces with or without teeth.
(1) V-belt without tooth width, without tooth on top and bottom
(2) Internally toothed wide V-belt with equally spaced transverse teeth on the bottom surface
(3) Wide V-belt with inner and outer teeth, with equidistant transverse teeth on both the top and bottom surfaces
(4) Truncated cone wide V-belt
structure
(1) The toothless V-belt is composed of a cloth covering layer, an extension rubber layer, a strength layer, a compression rubber layer and other components.
(2) The inner toothed wide V-belt is composed of stretch canvas layer (top cloth), stretch rubber layer, strength layer, compression rubber layer, tooth bottom cloth and other components.
(3) The inner and outer toothed wide V-belts are composed of tooth top cloth, stretch rubber layer, strength layer, compression rubber layer and tooth bottom cloth.
(4) The truncated cone-shaped wide V-belt is composed of a cloth covering layer, a stretch adhesive layer, a strong layer, a compression adhesive layer and other components
The role of each part
(1) The top cloth is composed of two or more layers of 45° diagonal rubber canvas. Its function can increase the lateral stiffness of the wide V-belt and obtain proper tensile properties.
(2) The tooth cloth includes the tooth bottom cloth and the tooth top cloth. Whether it is tooth bottom cloth or tooth top cloth, its function is to reduce tooth root cracks.
Other parts are basically the same as ordinary V-belts.
Banded V-belt
The combined V-belt is a V-belt group formed by joining the top surfaces of several identical ordinary V-belts or narrow V-belts together.
Structural features
(1) The link layer is composed of cords with a certain strength and rubber with sufficient elasticity. It can not only connect the V-belts together to make them a whole, but also adapt to the changes in the geometrical shape and dimensional error of the pulley grooves, so that each V-belt can be in good contact with the pulley grooves as much as possible, and give full play to each The ability of a V-belt. However, the machining accuracy of the pulley is higher. If the size error of the pulley groove is large, the pitch diameter of each pulley groove will be inconsistent, which may not only reduce the transmission capacity due to the additional stress generated by the mutual restraint between the belts, but also cause the connecting layer to break. .
(2) The connecting layer can reduce the non-uniform vibration of each single V-belt to a minimum by forming mutual cancellation, and imparting lateral rigidity and stability to each root through the combination, thereby eliminating the vibration phenomenon of each single root. Therefore, the joint belt is not easy to shake, slap and turn the belt. The stability of the horizontal direction between the belts is good, and it is not easy to drop the belt and not interfere with each other during operation. It is suitable for the occasion of pulsating load, especially suitable for parallel shaft transmission on vertical ground.
(3) There is a vertical plane on the inner side of the upper part of the adjacent two V-belts of the connected V-belt, so that there is enough space between the connecting layer and the outer circle of the pulley, which can not only avoid the contact friction between the connecting layer and the pulley , can also accommodate debris. If the arched connecting layer is used, this feature can be brought into play. It can also increase the flexibility of each V-shaped insert into the wheel groove, and compensate for the influence of the pitch error between the wheel grooves.
(4) The combined V-belt is composed of a set of belts of the same material and one-time molding and vulcanization. Each V-belt has the same length and has good integrity. Each belt is uniformly stressed and runs smoothly, so the bearing capacity is high. Long life, suitable for high power transmission.
The combined V-belt can be composed of 2~5 ordinary V-belts or narrow V-belts, depending on the conditions of use.