Komatsu Excavator Rotary Priority Valve is located next to the rotary operating spool in the five-way change-over valve. When the swing device and the bucket rod are operated at the same time, most of the pressure oil flows to the less loaded bucket rod, while the flow to the swing oil circuit decreases, so the bucket rod moves faster than the swing rod, which makes the joint operation difficult. The function of the rotary priority valve is to limit the pressure oil flow to the bucket rod-low speed control valve during combined operation, which limits the speed of the bucket rod and improves the combined operation performance. Its working principle is shown in Fig. 2-16.
(1) When the rotary lever is in the middle position, there is no pilot pressure oil from the travel shuttle valve and the rotary priority valve does not work. At this point, the pressure oil from the former main pump flows through the port Pa to the bucket rod-low speed control valve.
(2) When operating the rotary device. The pilot pressure oil from the travel shuttle valve pushes the sliding valve of the rotary priority valve to the left. Therefore, the pressure oil from the former main pump is throttled when it flows to the bucket rod-low speed operating valve through the Pa port, and the speed of the bucket rod is controlled, which improves the performance of the combined operation.
