为了提高拖拉机的生产率、經济性和使用方便性,必須增加变速箱的排档数和扩大变速范围。目前,六档以上的变速箱已在新生产的拖拉机上占絕大多数,它們几乎毫无例外地采用了“組成式”的結构。 組成式变速箱包括两个变速部分,其中档数較多者称为“主变速部分”,档数較少者称为“副变速部分”。副变速部分通常只有两个档,其中传动比較小者称为“高档”,較大者称为“低档”。主、副变速部分公用的齿輪称为“公用齿輪”。 In order to improve tractor productivity, economy and ease of use, it is necessary to increase gearbox gear and increase the speed range. At present, gearboxes above the sixth gear have accounted for the overwhelming majority of newly-produced tractors, and they have adopted “compositional” structures almost without exception. The composition of the gearbox consists of two variable speed parts, of which the number of gear is more known as the “main transmission part”, the less the number is called the “auxiliary transmission part.” Vice-speed part of the usually only two files, of which the smaller transmission ratio is called “high-grade”, the greater is called “low-grade.” The main, deputy variable speed part of the common gear called “common gear.”