PROBLEM TO BE SOLVED: To provide a steering hydraulic circuit that prevents the occurrence of surge pressure of a hydraulic clutch cylinder in the turning of a combine, thereby reducing a turning shock.SOLUTION: A steering hydraulic circuit of a combine operates a clutch cylinder (14) for steering by the switching operation of an electromagnetic switching valve (13). A pilot throttling valve (15) switched from a completion state to a diaphragm state when the pilot pressure of a supply oil passage exceeds a predetermined pressure is provided between the clutch cylinder (14) for steering and the electromagnetic switching valve (13). Or, a throttled check valve (23) for making a return oil flow into the oil passage to a tank when a return pressure of an oil return path exceeds the predetermined pressure is provided between the clutch cylinder (14) for steering and the electromagnetic switching valve (13).COPYRIGHT: (C)2015,JPO&INPIT【課題】コンバインの旋回時における油圧クラッチシリンダのサージ圧の発生を防いで旋回ショックを低減する操向油圧回路とする。【解決手段】電磁切換弁(13)の切換作動で操向用クラッチシリンダ(14)を作動させるコンバインの操向油圧回路において、前記操向用クラッチシリンダ(14)と電磁切換弁(13)との間に供給油路のパイロット圧が所定圧を越えると全通状態から絞り状態に切り換わるパイロット絞り切換弁(15)を設ける。または、操向用クラッチシリンダ(14)と電磁切換弁(13)との間に返油路の戻り圧が所定圧を越えると戻り油をタンクへの油路に流すスロットルチェック弁(23)を設ける。【選択図】図1
