Abstract: Gear transmission is the most important transmission method in agricultural machinery. There are many factors that affect gears. From the overall composition, there are mainly parts such as gearboxes, bearings, and shafts. From the manufacturing accuracy and assembly accuracy of the parts, Look, the design of parts is related to material selection and heat treatment, and the use is related to the maintenance and lubrication of gears. The gear transmission rate of agricultural machinery is relatively large, and it often operates under heavy loads and low speeds. The working conditions are relatively harsh, and maintenance is not standardized enough, which can easily lead to gear transmission failure and malfunction. The article analyzes the failure determination and maintenance methods of agricultural machinery gears for reference.
Keywords: agricultural machinery; gears; failure determination; maintenance
Gear transmission is the most important transmission method in agricultural machinery. There are many factors that affect gears. From the overall composition, there are mainly parts such as gearboxes, bearings, and shafts. From the perspective of the manufacturing accuracy and assembly accuracy of the parts, The design of parts is related to material selection and heat treatment, and the use is related to the maintenance and lubrication of gears. The gear transmission rate of agricultural machinery is relatively large, and it often operates under heavy loads and low speeds. The working conditions are relatively harsh, and maintenance is not standardized enough, which can easily lead to gear transmission failure and malfunction. The article analyzes the failure determination and maintenance methods of agricultural machinery gears for reference.
01 Reasons for gear failure
1.1 Broken teeth
1) Broken due to overload. Short-term overloading, overloading, or severe load concentration on the contact line may cause the gear to break due to overload. Overload The following situations may cause gear breakage: overload of the gear due to bearing damage; sudden impact overload; foreign matter between the two paired gears causing overload; bending of the shaft itself causing overload. When overload causes the gear to break, the cross section will appear in a coarse-grained shape. This situation usually occurs in high-hardness steel gears or cast iron gears, eventually leading to gear breakage.
2) Fatigue fracture. Once the material alternating ability at the tooth root reaches the fatigue limit, fatigue cracks will appear in the tooth root fillet, and the cracks will expand rapidly, eventually causing the gear to bend and break. The contact line between the helical cylindrical gear and the herringbone gear is tilted. The tooth root cracks in the two gears usually expand in the direction of the tilt. The broken surface is relatively smooth, and a shell-like pattern can be seen around the crack.
1.2 Tooth surface gluing
In the case of low-speed gear transmission, the contact of the gear itself is not good or the shape of the tooth surface is irregular, resulting in the normal local pressure on the tooth surface being too large to form a lubricating oil film on the gear surface, or the viscosity of the lubrication itself is too low, forming The thickness of the oil film is not enough, which causes the metal between the tooth surfaces to come into direct contact, causing local high temperature and welding, and at the same time tearing along the sliding direction to produce grooves. This is cold gluing. Tooth surface gluing usually occurs during the transmission process of tempered gears. Under the condition of high speed and heavy load of the gear, the local temperature may rise instantaneously, which may cause the oil film to rupture, the metal on the two contact surfaces to weld, and at the same time tear along the sliding direction to produce grooves. This is thermal gluing.
1.3 Tooth surface wear
Tooth flank wear can be defined as the loss of material on the tooth contact surface. If dust or dirt is mixed into the meshing area, the tooth surface will also be damaged at the sliding speed. This kind of wear is called abrasive wear. Excessive tooth thickness wear will lead to breakage. According to the wear mechanism, wear is divided into abrasive wear, scratches, corrosive wear, and wear caused by insufficient lubricating oil. Among them, destructive wear is usually caused by problems with the use of lubricating oil or improper selection of materials for the designed gears and gears themselves.
1.4 Tooth surface burns
Tooth surface burns are mainly caused by excessive friction caused by overloading, overspeeding or inappropriate lubricating oil, which in turn causes local temperature increases. Excessive local temperature can cause the quenched steel to become discolored, over-tempered or re-quenched, and the rate of fatigue failure at the burnt location will also be accelerated.
1.5 Plastic deformation of tooth surface
Under the influence of heavy load, the yield of the surface metal will cause plastic deformation on the surface. Short-term overload or an increase in the tooth surface friction coefficient will cause the surface metal of the soft tooth surface to flow along the sliding direction, leading to plastic deformation. . After plastic deformation occurs on the working surface of the gear, the main appearance features are wrinkled deformation, corrugated deformation, collapse and flash deformation. The main causes of plastic deformation on gear tooth surfaces are improper heat treatment, overloading and improper lubrication.
02. Correct maintenance method of transmission gears
2.1 Choose the right lubricant
In the transmission of gears, lubricating oil is an indispensable lubricating medium, which can protect the gear teeth and avoid damage. Transmission gears have special requirements for the viscosity of lubricating oil. If the viscosity is too low, a protective film will not be formed and the meshing surface of the gear teeth will not be protected. If the viscosity is too high, the transmission gears will lose friction and the temperature will be too low. It also cannot be started. In addition, under heavy load and high-speed operation, the oil temperature on the gear surface is too high, which can easily lead to oxidation and deterioration. Under high temperature conditions, gear oil has good anti-oxidation and stability properties, and standard specifications of lubricating oil must be used to ensure that the gear of antioxidant properties.
2.2 Ensure the gear surface is clean
When using agricultural machinery and large agricultural equipment, it is necessary to avoid overloading, ensure the sealing of the gear transmission system, and prevent hard objects and dust from entering the gear box.
2.3 When replacing accessories, choose original parts.
Due to the different processing methods, production standards and selected materials of non-original parts, the factory parts cannot meet the requirements, and they will not achieve the expected results after repair. They are likely to malfunction during use. When selecting gears, be sure to pay attention to the roughness of the gear surface. Relevant studies have found that the surface roughness of low-speed and heavy-loaded gears will cause greater wear on the gear surface, and the roughness of the initial part surface is higher. The higher the chance of wear, be sure to choose gears with smooth surfaces.
03 Conclusion
After replacing and maintaining the failed gears of agricultural machinery, they must be run-in before use to ensure that no wear occurs during use. In addition, the surface quality of new gears must be continuously improved to increase the load-bearing capacity and wear resistance of the gears, thereby extending the service life of agricultural machinery.
2024 February 4th Week VAFEM Product Recommendation:
A linear-motion bearing or linear slide is a bearing designed to provide free motion in one direction. There are many different types of linear motion bearings. Motorized linear slides such as machine slides, X-Y tables, roller tables and some dovetail slides are bearings moved by drive mechanisms. Not all linear slides are motorized, and non-motorized dovetail slides, ball bearing slides and roller slides provide low-friction linear movement for equipment powered by inertia or by hand. All linear slides provide linear motion based on bearings, whether they are ball bearings, dovetail bearings, linear roller bearings, magnetic or fluid bearings. X-Y tables, linear stages, machine slides and other advanced slides use linear motion bearings to provide movement along both X and Y multiple axis.
2024-02-21