Abstract: Triangular belts are widely used in agricultural machinery due to their unique advantages. Improper use and maintenance often lead to malfunctions, affecting the normal use of agricultural machinery. Therefore, the key points for the use and maintenance of triangular belt transmission are emphasized.

Keywords: agricultural machinery; Belt drive; use; maintenance

When the distance between the two transmission shafts is quite far, the transmitted power is not too large, and the transmission speed ratio of the two shafts does not need to be constant, belt transmission can be used. A small tractor powered by a single cylinder horizontal diesel engine relies mostly on a V-belt transmission device for power transmission between the engine and clutch; The power of the engine of the water field tillage machine is also transmitted to the gearbox through a V-belt. The V-belt not only has a buffering and vibration absorbing effect, but also can automatically slip when the tractor is overloaded, protecting the engine and the entire transmission system components from damage.

Overview of Belt Transmission

(1) Types of belts. Belts are classified according to their constituent materials, including cow belts, canvas rubber belts, and steel belts. Compared with cow leather belts, canvas rubber belts have more uniform tensile strength, better resistance to moisture and dryness, and are cheaper and more widely used. However, their disadvantage is that they are not as durable as cow leather belts. Steel belt is made of tough steel, which transmits high horsepower, high speed, and light weight, but has strict installation requirements. If divided by the cross-section of the belt, there are three types: flat belt, triangular belt, and circular belt. Flat belt transmission has a simple structure Z and is easy to manufacture with pulleys. It is more commonly used when the distance between the two transmission shafts is far, that is, when the distance between the transmission centers is large. Circular belts are used to transmit small power and are commonly used in textile machinery. Triangular belt transmission is generally used in agricultural machinery.

(2) Triangle belts can transmit a large amount of power, have a compact structure, allow for a large transmission ratio, are relatively safe, have good performance, and are inexpensive. Therefore, in agricultural machinery, triangle belt transmission is widely used. This type of belt has been standardized and mass-produced in the country. Different models have different specifications and sizes, so special attention should be paid when replacing them to avoid buying the wrong one.

(3) The principle of V-belt transmission. The V-belt drive operates by tightening the V-belt onto the grooves of two pulleys with a certain initial tension. When the active pulley rotates under power drive, it transmits power to the driven pulley through a V-belt. The cross-section of the V-belt is an isosceles trapezoid, and its working surface is the two sides in contact with the pulley groove. Under the same initial tension, the V-belt can generate greater frictional force than the flat belt transmission, thus having greater traction capacity.

The use and maintenance of the V-belt transmission device

Choosing the wrong model, specification, and size of the V-belt, installing fewer V-belts or mixing old and new ones, and making mistakes in the installation and adjustment of transmission mechanism components can all cause wear or damage to the V-belt and transmission mechanism components. Failure to inspect and maintain the transmission mechanism in a timely manner can cause dry friction in the bearings, pulley misalignment, and exacerbate wear and damage. If the machine is parked for a long time and the triangular belt is not removed and properly stored, it will often be parked outdoors and exposed to ice, snow, wind and rain, as well as the scorching sun, or stored in a warehouse, which can also cause deformation and damage to the belt. To correctly use and maintain the V-belt transmission device, the following points must be noted:

(1) Regularly check and adjust the tension of the V-belt. The V-belt needs to have a certain degree of tension during use. If the belt is too loose, it will cause the belt to slip and reduce transmission efficiency; The belt is too tight, which increases the consumption of engine power, exacerbates belt wear, and increases the radial force on the bearings of the two pulleys, leading to increased bearing wear. If the belt is too loose or too tight, adjust the adjusting bolt at the front of the frame to change the front and rear position of the pulley on the frame, so that the belt tension is appropriate.

(2) Check if the centerlines of the two pulley shafts are parallel, if the corresponding pulley grooves are aligned, and if there is any deviation. If the two axes are not parallel, it will cause uneven tension of the belt, leading to the phenomenon of "biting edges" in the V-belt, exacerbating the wear of the V-belt, and in severe cases, the V-belt may fall off. During work, it is found that the pulley is swaying. The cause should be identified, whether it is due to improper installation or deformation of the pulley and shaft, or large bearing displacement. Timely maintenance and resolution should be carried out to reduce wear on the V-belt and related components.

(3) Regularly replace the V-belt. When replacing a new V-belt, the tightening wheel, frame fixing bolts, and adjusting bolts should be loosened first. By rotating the main pulley, the V-belt should be turned into the pulley groove one by one. After checking and adjusting the tension, tighten the fixing bolts. To avoid prying the belt randomly with a screwdriver or iron rod and reduce damage to the belt and components during installation. When replacing, the appropriate type of belt should be selected strictly according to regulations. Meanwhile, in general, it is advisable to avoid reducing the number of belts as much as possible. When the belt is severely worn and needs to be replaced, several belts should be replaced simultaneously. New and old belts should not be mixed, otherwise it will cause increased wear and shorten the service life of the newly replaced belt.

(4) Triangle belts cannot be waxed. Due to the drawbacks of unstable transmission ratio and sometimes severe loss of revolutions in V-belt transmission, some people have strict requirements for transmission speed and use anti slip measures such as waxing to reduce loss of revolutions in areas with high transmission loads. This approach is unreasonable. Triangle belt transmission and flat belt transmission, although both rely on friction to transmit power, have different friction surfaces for transmitting power. A V-belt transmits power through friction between its two sides and grooves. Due to the non mechanical meshing transmission of general belt drives, no matter how large the wrap angle and initial tension of the belt drive are, and no matter how waxed and anti-skid it is, the slipping phenomenon between the belt and the groove during transmission is always inevitable. In addition, the commonly used structure of V-belts, whether it is a curtain structure or a rope structure, has layered sides. So, after the relative sliding between the pulley and the belt, due to the different speeds at the contact points between the belt groove and each layer of the belt, it is easy for the adhesive between the layers to peel off. It is evident that the higher the coefficient of friction, the greater the interlayer tearing force. Especially belts that have been used for a period of time are more prone to slipping than new belts. The rubber and cladding on its side have worn out, even revealing layers. When waxed to prevent slipping (although it cannot be completely non slip), it is more prone to tearing between layers. The belt, which could have been used before, has lost its application value due to peeling after waxing. So the V-belt must not be waxed like a flat belt to prevent loss of speed and increase its ability to transmit power.

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