HYDRAULIC CIRCUIT FOR LIFTING AND LOWERING REAPING PART OF COMBINE HARVESTER

摘要

The purpose of the present invention is to reduce a time lag generated when lowering a reaper at high speed. To this end, a hydraulic circuit comprise: a pilot-operated check valve (11); a first switching valve (7); a first throttle (9) which is connected to the first switching valve (7) in parallel and restricts the flow of hydraulic fluid supplied from a hydraulic pump (4) to a hydraulic cylinder (2); a resistance valve (10) which is connected to the first throttle (9) in series and opens a valve when a primary fluid pressure reaches a predetermined pressure; a second throttle (12b) for restricting the flow of hydraulic fluid which flows into the pilot-operated check valve (11) backward to be drained; a third throttle (18) which has a flow path sectional area smaller than the second throttle (12b) and restricts the flow of the drained hydraulic fluid; and a second switching valve (19) for selectively switching a flow path of the drained hydraulic fluid into a flow path of the hydraulic fluid drained through the third throttle (18).