Adaptive design of the hottest corn harvester

2022-07-30
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Adaptive design of corn harvester

Abstract: from the perspective of designers, this paper discusses the technical keys that should be paid attention to in the design of corn harvesters in China. The design idea of corn harvester suitable for China's national conditions is put forward, and the adaptive design of the harvester is discussed. The development direction of corn harvester technology was discussed

key words: adaptive design of corn harvester

introduction:

in the past 50 years, the development of agricultural machinery in New China can be summarized into three development stages: the development stage of farmland power in the 1950s and 1960s, the development stage of field machinery in the 1960s and 1980s, and the development stage of wheat and rice combine harvesters in the 1990s. So what is the next climax of China's agricultural machinery development: mechanized harvesting of corn

maize is one of the three major crops in China, with an annual planting area of 24.5 million hectares. If the yield is 50%, China needs about 100000 corn harvesters. The reality is that at present, the yield of corn machine is less than 2%, which is far lower than the 70% yield of wheat. The reason is multi-level, but from the design point of view, the low adaptability of the corn harvester is one of the main reasons

I. application status of foreign corn harvesters

the research and production technology of foreign corn harvesters has been mature. At present, in the United States, Germany, Ukraine, Russia and other western countries, corn harvesting (including grain and straw silage) has basically realized all mechanized operations. Because the planting method is mostly one season a year, and the moisture content of corn grain is very low at harvest, most countries adopt the harvesting method of corn ear picking and direct threshing. For example, most of the corn combine harvesters of John Deere company, case company, mengle company and DEUTZ company in the United States are equipped with a corn header on the wheat combine harvester, and the corn is jointly harvested by adjusting the rotation speed and threshing clearance of the threshing drum

in the past two decades, China has successively introduced some foreign models, such as the United harvester of case company of the United States, which can replace the corn header to complete the corn picking and threshing operations in one operation. Since the corn production areas in northern China, especially the wheat and corn rotation planting areas, have a grain moisture content of more than 35% when harvested, the direct threshing method is adopted for harvesting, and the grain crushing rate is very serious. According to the measurement at wanmufang test station in Luancheng County, Hebei Province in September, 1980, when the 1440 combine harvester of case company of the United States is replaced with the corn header, the grain crushing rate is 14% on average, and the maximum is 30%, The total loss rate reached 20%. Moreover, this direct threshing harvesting method is not conducive to the post ripening of corn, which reduces the yield, and the corn stalk cannot be crushed and returned to the field or recycled. Therefore, this kind of equipment is not suitable for the harvesting of high moisture content corn in the two crop rotation planting areas in China

relatively speaking, the kcky-6 corn harvester of Kherson combain combine harvester manufacturing company in Ukraine can perform the combined operation of ear picking, ear peeling and silage, which is suitable for the agronomic requirements of most regions in China. However, due to the large size of the machine, it has poor adaptability to the field roads in the vast rural areas of China. The price is expensive, which is inconsistent with the development level of China's economy

II. Development status of domestic corn harvesters

since the 1990s, many units in China have developed a variety of corn harvesters, with more than 60 models, and applied for 64 relevant patents. From the perspective of structure, there are mainly the following models:

a. side mounted and hanging corn harvester

side mounted and hanging on four-wheel tractor. The representative models include 4yzf-1, 4y118, etc., mostly single row corn harvester and ear picking roller type ear picking mechanism. Generally, it is equipped with straw crushing device, which can complete corn ear picking, header, straw crushing and other operations at one time

b wood based panel universal testing machine fixture includes internal bonding strength fixture, internal bonding strength fixture, static bending strength fixture, elastic modulus fixture, screw grip force fixture and surface bonding strength fixture The knapsack corn harvester

is used together with a tractor of 36.8 ~ 48kW (50-65hp). The ear picking mechanism of the two row machine is mostly of the ear picking roller type, which has a certain peeling function. The ear plucking mechanism of the three row machine is mostly a ear plucking plate. This model can complete corn ear picking, ear header and straw crushing in one operation

c. traction corn harvester

can be used with crawler or wheel tractors. The representative model is fengshou-2 horizontal traction corn harvester. For tractors with supporting power of 40 ~ 55kW (54 ~ 75HP) and above, the ear plucking mechanism is of ear plucking roller type and has the function of peeling. Because its unit is long and it needs to be manually opened before operation, it does not meet the requirements of large-scale operation, so it is rarely used at present

d. multi row self-propelled corn combine harvester

the representative models are 4YZ-3, 4yf-3 and 4yz-4. Most of these models are ear plucking plate type ear plucking mechanisms, and equipped with 58.8 ~ 88kw (80-120hp) engines, which can realize the functions of corn ear plucking, header and straw crushing. For example, the Fulu brand 4YZ-3 corn combine harvester can measure the tensile strength, elongation at break, modulus of elasticity, stress, strain and other parameters of materials. The main working parts are made by the Ukrainian Kherson kangbein company with advanced production technology, complete equipment and mature technology. Although the operating performance and quality are the same as those of domestic models, they have high reliability and have been recognized by users. Jinlang 4yjl-3 corn combine harvester is characterized by the combined structure of hob stalk pulling roller and ear picking plate, which avoids the phenomenon of weeds entanglement and reduces the power consumption of ear picking. The adaptability of machines and tools and the harvest quality are good. Due to the design of open and inverted fruit box, its working efficiency is increased by 30%

e. ear stem type corn harvester

there are two representative models: 4YZ-3 and 4yz-4. Model 4yz-4 is designed according to the principle of kcky-6 corn harvester of Kherson combain manufacturing company in Ukraine. It is a 4-row self-propelled type with the function of corn peeling. 4YZ-3 corn harvester is a three row self-propelled ear stem and harvest corn combine harvester with fruit box. The machine can meet the needs of the vast rural field roads and the operation of small and medium-sized plots in China. This machine can harvest green straw in time and achieve the purpose of harvesting both ears and stems

in the past decade, the voice of realizing mechanized corn harvest has been rising. The government, scientific research institutions and enterprises are optimistic about the corn harvest market, but the promotion effect of corn harvester is not good. There are many factors such as policy, planting pattern and so on. However, the poor adaptability of machines and tools is also one of the main reasons. The development of corn harvester suitable for China's national conditions has become a new focus of domestic corn harvester research

III. technical characteristics of China's corn harvesters

compared with developed countries such as Europe and the United States, China's corn planting has the following characteristics: 1. The planting plot is small; 2. The row spacing of corn planting is not uniform; 3. The grain moisture content during the corn harvest period is high. Therefore, the design requirements of corn harvesters in China this year are different from those in developed countries such as Europe and the United States. The following points should be achieved:

1. The designed corn harvester should be very flexible in the process of operation, transportation and grain unloading, and is suitable for use in small plots of fields

2. In view of the current low cultural quality of farmers, the developed corn harvester should be easy to operate and maintain as much as possible.

3. The designed corn harvester should be able to harvest in a wrong way. Otherwise, the harvest quality will be affected and the production efficiency will be reduced. This has affected the enthusiasm of farmers to buy corn harvesters

4. The designed corn harvester must be able to harvest high moisture corn (about 40% moisture content of kernels), and the crushing rate of ears and kernels shall not exceed the national standard

5. In order to prevent mildew, there should not be too many stems and leaves in the harvested corn ears

6. The unit shall have good strength and rigidity and be able to adapt to harsh field roads

7. The harvester can return the straw to the field with high quality at the same time

8. The unit has high reliability

IV. adaptive design of corn harvesters

we know that Chinese farmers buy corn harvesters not only to reduce labor intensity, but also to make money. Therefore, the designed corn harvesters must have high shift productivity and make users profitable. Therefore, improving the adaptability of machines and tools has become the key technology to realize the mechanized harvest of Maize in China

the adaptability design of the harvester should be considered from the following aspects

1. Determine a reasonable overall design scheme

different forms and different uses of corn harvesters adopt different configurations. Generally, the corn harvester with profit and tax of 208billion yuan is composed of header, elevator, ear box, etc. During the overall design, special attention shall be paid to the longitudinal and transverse stability of the whole machine, the rationality of the transmission system and the safety of operation and transportation. Considering the current situation of rural fields, roads and actual planting in China, the maximum speed of operation shall not exceed 6km/h, and the maximum speed of transportation shall not exceed 20km/h; In order for the engine to work under normal conditions and ensure the operation quality, 20 ~ 30% power reserve shall be considered for the supporting power. For example, the two row corn harvester requires 26-32kw power for harvesting ears and crushing straw. In addition, the walking power consumption is 6 ~ 8kw. Then total N = 32+6=38kw. Considering the factors such as transportation, transportation and power reserve, it is appropriate to select an engine with an engine power of 48kW

in the design, attention should also be paid to the matching of harvester and agronomy: for example, the harvester can open the road by itself without manual opening, and it should adapt to the existing rural management system; In the area of two crops a year, the crushing of straw and stubble should also be considered

2. Select appropriate ear plucking mechanism

ear plucking device is the heart of corn harvester. The requirements for ear plucking device are small grain loss, low grain crushing rate, few broken stems and sufficient ear plucking capacity

as we know, when the moisture content of the stem is high, because the stem is green and thick, the connecting force between the ear stalk and the stem is large. As the moisture content of the stem decreases, the connecting force between the two gradually decreases. However, as the moisture content of the stem continues to decline, the stem becomes relatively weak, and the connecting force between the ear stalk and the stem increases. When the stem becomes dry, the connecting force between the ear stalk and the ear reaches the minimum

at present, there are four different ear plucking methods for the ear plucking mechanism: A. six edge stick + ear plucking plate B, four edge knife + ear plucking plate C. dragon claw type ear plucking rod type, D, double stick combination type. In terms of structure, the characteristics of the stripping plate are: ① good rigidity, independent structure, convenient for multi row assembly; ② The broken rate of grain is low; ③ High power consumption. The characteristics of the ear picking roller mechanism are as follows: ① high ear cleaning rate; ② The transmission is complex and the weight of the unit is heavy; ③ The ear is large and the terminal grain is easy to be damaged at harvest. After more than ten years' research and analysis, the author believes that the factors affecting the operation quality are: the shape of the stripping roller, the diameter D of the roller, the length L, the rotating speed n, the shape of the stripping plate and the clearance δ And other relevant parameters. Shape of stripping roller, shape and clearance of stripping plate δ Especially important. The shape of the stripping roller mainly affects the grain crushing. Shape and clearance of stripping plate δ Affect whether the header works normally

the average diameter of stems of most Maize Varieties in China is 20mm, and the diameter of bracts at the big end of ears is 50mm. Based on this, the ears will be picked

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