变量式轴向柱塞泵的斜盘倾角为零时称为中位，此时泵的输出流量应为零。但有时会出现中位偏离调整机构中点的现象，在中点时仍有流量输出。其原因是控制器的位置偏离、松动或损伤，需要重新调零、紧固或更换。泵的角度维持力不够、倾斜角耳轴磨损也会产生这种现象。
When the swashplate angle of the variable axial piston pump is zero, it is called the middle position. At this time, the output flow of the pump should be zero. But sometimes the middle position deviates from the middle point of the adjustment mechanism, and there is still flow output at the middle point. The reason is that the position of the controller is deviated, loose or damaged, and it needs to be reset, tightened or replaced. This phenomenon can also occur if the angle maintaining force of the pump is not enough and the inclined angle trunnion is worn.