Agricultural machinery, such as rice and wheat threshers, plays a critical role in the rice and wheat harvest process. The speed control of the drum, its core component, directly impacts threshing efficiency, clean threshing rate, and grain integrity. Scientifically adjusting the drum speed can significantly optimize threshing performance, improving operation quality and economic benefits. The following analysis covers seven aspects: speed control principles, crop characteristic adaptation, power matching methods, dynamic adjustment strategies, comprehensive parameter coordination, common problem resolution, and technological development trends.
Drum speed control in rice and wheat threshers essentially optimizes threshing force and impact frequency by varying the relative speed between the threshing element and the crop. High speeds increase the impact force of the threshing teeth or ribs on the grains, enabling faster grain removal. However, excessive linear speeds can easily lead to grain breakage or excessive stalk fragmentation. Low speeds result in a gentler threshing process, but insufficient force can lead to incomplete threshing. Therefore, speed control must strike a balance between clean threshing rate, breakage rate, and energy consumption to ensure optimal threshing performance and machine life.
The varying physical properties of different crops require threshers to have flexible speed adaptation capabilities. The strength of the grain-husk bond, stem toughness, and moisture content of rice and wheat all influence threshing difficulty. For example, high-moisture wheat requires a lower speed to prevent grain flattening, while dry rice can be improved by increasing the speed appropriately. Furthermore, easy-to-thresh and difficult-to-thresh varieties have different speed sensitivities. The former can achieve high threshing rates at lower speeds, while the latter require increasing the speed to compensate for insufficient threshing element force. During operation, the speed must be dynamically adjusted based on the crop variety, maturity, and dryness to achieve precise threshing.
Agricultural rice and wheat threshers have diverse power sources, and speed adjustment methods vary accordingly. When powered by an electric motor, the speed is typically fixed, requiring pulley replacement or gear ratio adjustment to achieve speed matching. The formula "motor pulley diameter × motor speed = drum pulley diameter × drum speed" provides a theoretical basis for pulley selection. For internal combustion engines, such as those used in hand tractors, the throttle can be used to control the engine speed, indirectly adjusting the drum speed. This adjustment method offers high flexibility, but requires extensive operator experience to avoid unstable threshing due to speed fluctuations.
In practice, the drum speed must be adjusted in coordination with other parameters. For example, the gap between the drum and the concave plate directly affects threshing performance: if the gap is too small, high speeds can easily lead to grain breakage; if the gap is too large, low speeds can result in incomplete threshing. Therefore, when adjusting the speed, the concave plate gap should be checked to ensure it matches the speed. Furthermore, the fan air volume must be coordinated with the speed: at high speeds, increasing the air volume appropriately can improve cleaning efficiency, but it must prevent grains from being blown out of the machine; at low speeds, the air volume should be reduced to minimize entrainment losses.
Agricultural rice and wheat threshers can cause various problems during operation due to improper speed. If the speed is too high, the drum can easily clog, resulting in incomplete threshing or machine overload; if the speed is too low, threshing efficiency may decrease and increase the burden of subsequent cleaning. Operators should closely monitor threshing quality and adjust the speed promptly if they notice excessive amounts of unthreshed ears or stalks mixed in with the grains. At the same time, regular inspections of drum bearings, belts, and other components are necessary to prevent abnormal speeds caused by mechanical failures.
With the advancement of agricultural mechanization, speed control technology for rice and wheat threshers is evolving towards intelligent and precise control. New threshers use sensors to monitor parameters such as crop moisture content and drum load in real time, automatically adjusting speed to suit varying operating conditions. Furthermore, the introduction of continuously variable transmission technology enables smoother speed regulation, reducing the efficiency losses associated with traditional gear shifting or pulley replacement. These innovations not only enhance the adaptability and operating efficiency of threshers but also provide technical support for precision agriculture.
