Abstract:

Sieve is one of the important parts of corn grain harvester. However， it is often blocked by corn cobs in working process， which leads to high loss rate and high percentage of dirt corn kernels. The sieve with chaffer opening angle of 37.5°， 45°， 52.5° and 60° were selected as research objects. The stripping force test of blocking corn cob was carried out by using self-made device. The results show that the hole-blocking ratio of sieve gradually increases with the work quantity of corn grain harvester， and the dirt percentage in granary and the loss rate at the tail sieve varied slowly first and then increased sharply. The influence of sieve blocking on the quality of cleaning operation was significantly enhanced when work quantity of corn grain harvester exceeded 1.5 hm2. The hole-blocking ratio of upper sieve was 7.89%， 7.59%， 7.14% and 6.91%， respectively. The hole-blocking ratio of tail sieve was 8.07%， 7.81%， 7.49% and 6.78%， respectively. The dirt percentage of corn kernels in granary was 1.15%， 1.29%， 1.34% and 1.45%， respectively. The loss rate of corn kernels at the tail sieve was 1.13%， 1.07%， 0.93% and 0.87%， respectively. The stripping force of blocking corn cob in upper and tail sieve were all between 0.5~ 3.5 N. The average stripping force of blocking cob in upper sieve was 2.07 N， 1.76 N， 1.56 N and 1.47 N， respectively. The average stripping force of blocking cob in tail sieve was 2 N， 1.73 N， 1.59 N and 1.48 N， respectively.

Key words: agricultural engineering, corn grain harvester, sieve, blocking, corn cob, stripping